Methods for manufacturing three-dimensional devices and devices created thereby

ABSTRACT

In certain exemplary embodiments of the present invention, three-dimensional micro-mechanical devices and/or micro-structures can be made using a production casting process. As part of this process, an intermediate mold can be made from or derived from a precision stack lamination and used to fabricate the devices and/or structures. Further, the micro-devices and/or micro-structures can be fabricated on planar or nonplanar surfaces through use of a series of production casting processes and intermediate molds. The use of precision stack lamination can allow the fabrication of high aspect ratio structures. Moreover, via certain molding and/or casting materials, molds having cavities with protruding undercuts also can be fabricated.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, claims priority to, andincorporates by reference in its entirety U.S. application Ser. No.10/479,335, now U.S. Pat. No. 7,410,606, which claims priority to eachof:

International Application No. PCT/US2002/17936, filed 5 Jun. 2002;

U.S. Application Ser. No. 60/339,773, filed 17 Dec. 2001; and

U.S. Application Ser. No. 60/295,564, filed 5 Jun. 2001.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its wide variety of potential embodiments will be morereadily understood through the following detailed description, withreference to the accompanying drawings in which:

FIG. 1 is a flowchart of an exemplary embodiment of a method of thepresent invention.

FIG. 2 is a flow diagram of exemplary items fabricated using a method ofthe present invention.

FIG. 3 is a perspective view of an exemplary casting of the presentinvention that illustrates aspect ratio.

FIG. 4 is an assembly view of an exemplary assembly of the presentinvention.

FIG. 5A is a top view of an exemplary stack lamination mold of thepresent invention.

FIGS. 5B-5E are exemplary alternative cross-sectional views of anexemplary stack lamination mold of the present invention taken atsection lines 5-5 of FIG. 5A.

FIG. 6 is an unassembled cross-sectional view of an alternativeexemplary stack lamination mold taken of the present invention atsection lines 5-5 of FIG. 5A.

FIG. 7 is a cross-sectional view of an exemplary alternative stacklamination mold of the present invention taken at section lines 5-5 ofFIG. 5A.

FIG. 8 is a perspective view of an exemplary laminated mold.

FIG. 9 is a cross-section of an exemplary mold of the present inventiontaken along lines 9-9 of FIG. 8.

FIG. 10A is a top view an exemplary layer of the present inventionhaving a redundant array of shapes.

FIG. 10B is a top view of an exemplary layer of the present inventionhaving a non-redundant collection of shapes.

FIG. 11 is a top view of an exemplary stacked lamination mold of thepresent invention.

FIG. 12 is a cross-sectional view of an exemplary mold of the presentinvention taken at section lines 12-12 of FIG. 11.

FIG. 13 is a side view of an exemplary cast part of the presentinvention formed using the exemplary mold of FIG. 11.

FIG. 14 is a top view of an exemplary laminated mold of the presentinvention.

FIG. 15 is a cross-sectional view of an exemplary mold of the presentinvention taken at section lines 15-15 of FIG. 14.

FIG. 16 is a perspective view of an exemplary cast part of the presentinvention formed using the exemplary mold of FIG. 14.

FIG. 17 is a top view of an exemplary planar laminated mold of thepresent invention having an array of openings.

FIG. 18 is a top view of an exemplary flexible casting or mold insert ofthe present invention molded using the laminated mold of FIG. 17.

FIG. 19 is a top view of an exemplary mold fixture of the presentinvention

FIG. 20 is a top view of an exemplary planar laminated mold of thepresent invention.

FIG. 21 is a top view of an exemplary flexible casting or mold insert ofthe present invention molded using the laminated mold of FIG. 20.

FIG. 22 is a top view of an exemplary mold fixture of the presentinvention

FIG. 23 is a perspective view of an exemplary laminated mold of thepresent invention.

FIG. 24 is a close-up perspective view of an exemplary singlecylindrical cavity of an exemplary mold of the present invention.

FIG. 25 is a perspective view of an exemplary cast part of the presentinvention.

FIG. 26 is a flowchart of an exemplary method of the present invention.

FIG. 27 is a perspective view of a plurality of exemplary layers of thepresent invention.

FIG. 28 is a perspective view of an exemplary laminating fixture of thepresent invention.

FIG. 29 is a top view of stack lamination mold of the present inventionthat defines an array of cavities.

FIG. 30 is a cross-section of a cavity of the present invention takenalong section lines 30-30 of FIG. 29.

FIG. 31 is a perspective view of an exemplary single corrugated feedhornof the present invention.

FIG. 32 is a side view of an exemplary casting fixture of the presentinvention.

FIG. 33 is a side view of an exemplary section of cylindrical tubing ofthe present invention that demonstrates the shape of an exemplaryfluidic channel of the present invention.

FIG. 34 is a top view of an exemplary micro-machined layer of thepresent invention.

FIG. 35 is a cross-sectional view of a laminated slit of the presentinvention taken along section lines 35-35 of FIG. 34.

FIG. 36 is a side view of a portion of an exemplary flexible cavityinsert of the present invention.

FIG. 37 is a top view of an exemplary base plate of the presentinvention.

FIG. 38 is a front view of a single exemplary flexible cavity insertassembly of the present invention.

FIG. 39 is a front view of flexible cavity inserts of the presentinvention.

FIG. 40 is a top view of a top plate of the present invention.

FIG. 41 is a flowchart of an exemplary embodiment of a method of thepresent invention.

FIG. 42A is a top view of an exemplary laminated stack of the presentinvention.

FIG. 42B is a cross-sectional view, taken at section lines 42-42 of FIG.42A, of an exemplary laminated stack of the present invention.

FIG. 43 is side view of an exemplary mold and casting of the presentinvention.

FIG. 44 is a top view of an exemplary casting fixture of the presentinvention.

FIG. 45 is a front view of the exemplary casting fixture of FIG. 44.

FIG. 46 is a top view of a portion of an exemplary grid pattern of thepresent invention.

FIG. 47 is an assembly view of components of an exemplary pixelatedgamma camera of the present invention.

FIG. 48A is a top view of an array of generic microdevices of thepresent invention.

FIG. 48B is a cross-sectional view of an exemplary microdevice of thepresent invention, taken at section lines 48-48 of FIG. 48A, in the openstate.

FIG. 49 is a cross-sectional view of the exemplary microdevice of FIG.48B, taken at section lines 48-48 of FIG. 48A, in the closed state.

FIG. 50 is a cross-sectional view of an alternative exemplarymicrodevice of the present invention, taken at section lines 48-48 ofFIG. 48A, and shown with an inlet valve open.

FIG. 51 is a cross-sectional view of the alternative exemplarymicrodevice of FIG. 50, taken at section lines 48-48 of FIG. 48A, andshown with an outlet valve open.

FIG. 52 is a top view of an exemplary microwell array of the presentinvention.

FIG. 53 is a cross-sectional view taken at lines 52-52 of FIG. 52 of anexemplary microwell of the present invention.

FIG. 54 is a cross-sectional view taken at lines 52-52 of FIG. 52 of analternative exemplary microwell of the present invention.

FIG. 55 is a top view of exemplary microwell of the present invention.

FIG. 56 is a cross-sectional view of an exemplary microwell of thepresent invention, taken at lines 55-55 of FIG. 55.

DETAILED DESCRIPTION

Certain exemplary embodiments of the present invention can combinecertain techniques of stack lamination with certain molding processes tomanufacture a final product. As a result of the stack laminationtechniques, precision micro-scale cavities of predetermined shapes canbe engineered into the stack lamination. Rather than have the stacklamination embody the final product, however, the stack lamination canbe used as an intermediate in a casting or molding process.

In certain exemplary embodiments of the present invention, the stacklamination (“laminated mold”) can be made up of layers comprisingmetallic, polymeric, and/or ceramic material. The mold can be a positivereplication of a predetermined end product or a negative replicationthereof. The mold can be filled with a first cast material and allowedto solidify. A first cast product can be demolded from the mold. Thefirst cast material can comprise a flexible polymer such as siliconerubber.

Certain exemplary embodiments of a method of the present invention canfurther include surrounding the first cast product with a second castingmaterial and allowing the second cast material to solidify. Stillfurther, a second cast product can be demolded from the first castproduct.

Some exemplary embodiments of the present invention can further includepositioning an insert into the cavity prior to filling the mold with thefirst cast material, wherein the insert occupies only a portion of thespace defined by the cavity. The second cast product can be nonplanar.The end product and/or the mold cavity can have an aspect ratio greaterthat 100:1. The end product can be attached to the substrate or it canbe a free-standing structure.

FIG. 1 is a flowchart of an exemplary embodiment of a method 1000 of thepresent invention. At activity 1010, a mold design is determined. Atactivity 1020, the layers of the mold (“laminations”) are fabricated. Atactivity 1030, the laminations are stacked and assembled into a mold (aderived mold could be produced at this point as shown in FIG. 1). Atactivity 1060, a first casting is cast. At activity 1070, the firstcasting is demolded.

FIG. 2 is a flow diagram of exemplary items fabricated during a method2000 of the present invention. Layers 2010 can be stacked to form a moldor stacked lamination 2020. A molding or casting material can be appliedto mold 2020 to create a molding or casting 2030, that can be demoldedfrom mold 2020.

FIG. 3 is a perspective view of an exemplary molding 3000 of the presentinvention that demonstrates a parameter referred to herein as “aspectratio” which is described below. Molded block 3010 has numerousthrough-holes 3020, each having a height H and a diameter or width W.For the purposes of this application, aspect ratio is defined as theratio of height to width or H/W of a feature, and can apply to any“negative” structural feature, such as a space, channel, through-hole,cavity, etc., and can apply to a “positive” feature, such as a wall,projection, protrusion, etc., with the height of the feature measuredalong the Z-axis. Note that all features can be “bordered” by at leastone “wall”. For a positive feature, the wall is part of the feature. Fora negative feature, the wall at least partially defines the feature.

FIG. 3 also demonstrates the X-, Y-, and Z-directions or axes. For thepurposes of this application, the dimensions measured in the X- andY-directions define a top surface of a structure (such as a layer, astack lamination mold, or negative and/or positive replications thereof)when viewed from the top of the structure. The Z-direction is the thirddimension perpendicular to the X-Y plane, and corresponds to the line ofsight when viewing a point on a top surface of a structure from directlyabove that point.

Certain embodiments of a method of the present invention can controlaspect ratios for some or all features in a laminated mold, derivedmold, and/or cast item (casting). The ability to attain relatively highaspect ratios can be affected by a feature's geometric shape, size,material, and/or proximity to another feature. This ability can beenhanced using certain embodiments of the present invention. Forexample, through-features of a mold, derived mold, and/or final part,having a width or diameter of approximately 5 microns, can have adimension along the Z axis (height) of approximately 100 microns, orapproximately 500 microns, or any value in the range there between(implying an aspect ratio of approximately 20:1, 100:1, or any value inthe range therebetween, including, for example:

20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 60:1, 20:1 to 70:1,20:1 to 80:1, 20:1 to 90:1, 20:1 to 100:1,

30:1 to 40:1, 30:1 to 50:1, 30:1 to 60:1, 30:1 to 70:1, 30:1 to 80:1,30:1 to 90:1, 30:1 to 100:1,

40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 40:1 to 90:1,40:1 to 100:1,

50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 50:1 to 90:1, 50:1 to 100:1,

60:1 to 70:1, 60:1 to 80:1, 60:1 to 90:1, 60:1 to 100:1,

70:1 to 80:1, 70:1 to 90:1, 70:1 to 100:1,

80:1 to 90:1, 80:1 to 100:1, etc).

As another example, a through slit having a width of approximately 20microns can have a height of approximately 800 microns, or approximately1600 microns, or any value in the range therebetween (implying an aspectratio of approximately 40:1, 80:1, or any value in the rangetherebetween, including, for example:

40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1,

50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1,

60:1 to 70:1, 60:1 to 80:1,

70:1 to 80:1, etc).

As yet another example, the same approximately 20 micron slit can beseparated by an approximately 15 micron wide wall in an array, where thewall can have a dimension along the Z axis (height) of approximately 800microns, or approximately 1600 microns, or any value in the rangetherebetween (implying an aspect ratio of approximately 53:1, 114:1, orany value in the range therebetween, including, for example:

53:1 to 60:1, 53:1 to 70:1, 53:1 to 80:1, 53:1 to 90:1, 53:1 to 100:1,53:1 to 110:1, 53:1 to 114:1,

60:1 to 70:1, 60:1 to 80:1, 60:1 to 90:1, 60:1 to 100:1, 60:1 to 10:1,60:1 to 114:1,

70:1 to 80:1, 70:1 to 90:1, 70:1 to 100:1, 70:1 to 110:1, 70:1 to 114:1,

80:1 to 90:1, 80:1 to 100:1, 90:1 to 110:1, 90:1 to 114:1,

90:1 to 100:1, 90:1 to 110:1, 90:1 to 114:1,

100:1 to 110:1, 100:1 to 114:1, etc.).

Still another example is an array of square-shaped openings having sidesthat are approximately 0.850 millimeters wide, each opening separated byapproximately 0.150 millimeter walls, with a dimension along the Z axisof approximately 30 centimeters. In this example the approximately 0.850square openings have an aspect ratio of approximately 353:1, and theapproximately 0.150 walls have an aspect ratio of approximately 2000:1,with lesser aspect ratios possible. Thus, the aspect ratio of theopenings can be approximately 10:1, or approximately 350:1, or any valuein the range therebetween, including for example:

10:1 to 20:1, 10:1 to 30:1, 10:1 to 40:1, 10:1 to 50:1, 10:1 to 60:1,10:1 to 70:1, 10:1 to 80:1, 10:1 to 90:1, 10:1 to 100:1, 10:1 to 150:1,10:1 to 200:1, 10:1 to 250:1, 10:1 to 300:1, 10:1 to 350:1,

20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 60:1, 20:1 to 70:1,20:1 to 80:1, 20:1 to 90:1, 20:1 to 100:1, 20:1 to 150:1, 20:1 to 200:1,20:1 to 250:1, 20:1 to 300:1, 20:1 to 350:1,

30:1 to 40:1, 30:1 to 50:1, 30:1 to 60:1, 30:1 to 70:1, 30:1 to 80:1,30:1 to 90:1, 30:1 to 100:1, 30:1 to 150:1, 30:1 to 200:1, 30:1 to250:1, 30:1 to 300:1, 30:1 to 350:1,

40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 40:1 to 90:1,40:1 to 100:1, 40:1 to 150:1, 40:1 to 200:1, 40:1 to 250:1, 40:1 to300:1, 40:1 to 350:1,

50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 50:1 to 90:1, 50:1 to 100:1,50:1 to 150:1, 50:1 to 200:1, 50:1 to 250:1, 50:1 to 300:1, 50:1 to350:1,

75:1 to 80:1, 75:1 to 90:1, 75:1 to 100:1, 75:1 to 150:1, 75:1 to 200:1,75:1 to 250:1, 75:1 to 300:1, 75:1 to 350:1,

100:1 to 150:1, 100:1 to 200:1, 100:1 to 250:1, 100:1 to 300:1, 100:1 to350:1,

150:1 to 200:1, 150:1 to 250:1, 150:1 to 300:1, 150:1 to 350:1,

200:1 to 250:1, 200:1 to 300:1, 200:1 to 350:1,

250:1 to 300:1, 250:1 to 350:1,

300:1 to 350:1, etc.

Moreover, the aspect ratio of the walls can be approximately 10:1, orapproximately 2000:1, or any value in the range therebetween, includingfor example:

10:1 to 20:1, 10:1 to 30:1, 10:1 to 40:1, 10:1 to 50:1, 10:1 to 100:1,10:1 to 200:1, 10:1 to 500:1, 10:1 to 1000:1, 10:1 to 2000:1,

20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 100:1, 20:1 to 200:1,20:1 to 500:1, 20:1 to 1000:1, 20:1 to 2000:1,

30:1 to 40:1, 30:1 to 50:1, 30:1 to 100:1, 30:1 to 200:1, 30:1 to 500:1,30:1 to 1000:1, 30:1 to 2000:1,

40:1 to 50:1, 40:1 to 100:1, 40:1 to 200:1, 40:1 to 500:1, 40:1 to1000:1, 40:1 to 2000:1,

50:1 to 100:1, 50:1 to 200:1, 50:1 to 500:1, 50:1 to 1000:1, 50:1 to2000:1,

100:1 to 200:1, 100:1 to 500:1, 100:1 to 1000:1, 100:1 to 2000:1,

200:1 to 500:1, 200:1 to 1000:1, 200:1 to 2000:1,

500:1 to 1000:1, 500:1 to 2000:1,

1000:1 to 2000:1, etc.

Another example of aspect ratio is the space between solid (positive)features of a mold, derived mold, and/or casting. For example, as viewedfrom the top, a casting can have two or more solid rectangles measuringapproximately 50 microns wide by approximately 100 microns deep with anapproximately 5 micron space therebetween (either width-wise ordepth-wise). The rectangles can have a height of 100 microns, or 500microns, or any value in the range therebetween (implying an aspectratio of 20:1, or 100:1, or any value therebetween, including, forexample:

20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 60:1, 20:1 to 70:1,20:1 to 80:1, 20:1 to 90:1, 20:1 to 100:1,

30:1 to 40:1, 30:1 to 50:1, 30:1 to 60:1, 30:1 to 70:1, 30:1 to 80:1,30:1 to 90:1, 30:1 to 100:1,

40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 40:1 to 90:1,40:1 to 100:1,

50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 50:1 to 90:1, 50:1 to 100:1,

60:1 to 70:1, 60:1 to 80:1, 60:1 to 90:1, 60:1 to 100:1,

70:1 to 80:1, 70:1 to 90:1, 70:1 to 100:1,

80:1 to 90:1, 80:1 to 100:1, etc).

In another example the same rectangles can have a space there between ofapproximately 20 microns, and the rectangles can have dimensions alongthe Z axis of approximately 800 microns, or approximately 5000 microns,or any value therebetween (implying an aspect ratio of approximately40:1, or 250:1, or any value therebetween, including, for example:

40:1 to 50:1, 40:1 to 75:1, 40:1 to 100:1, 40:1 to 150:1, 40:1 to 200:1,40:1 to 250:1,

75:1 to 100:1, 75:1 to 150:1, 75:1 to 200:1, 75:1 to 250:1,

100:1 to 150:1, 100:1 to 200:1, 100:1 to 250:1,

150:1 to 200:1, 150:1 to 250:1,

200:1 to 250:1, etc).

FIG. 4 is an assembly view of an exemplary assembly 4000 of the presentinvention that includes mold 4010 and cast part 4020 formed from mold4010. Because certain exemplary embodiments of the present invention canutilize lithographically-derived micro-machining techniques (or in somecases, non-lithographically-derived micro-machining techniques, such aslaser machining) combined with molding and/or casting, laminated moldscan be conceived as negatives 4010 or positives 4020 of the desired endproduct. The terms “negative” or “positive” replications can besubjective terms assigned to different stages of reaching an endproduct. For certain embodiments, any intermediate or the end productcan be considered a negative or positive replication depending on asubject's point of view. For the purpose of this application, a“positive’ replication is an object (whether an intermediate or an endproduct) that geometrically resembles at least a portion of the spatialform of the end product. Conversely, a “negative” replication is a moldthat geometrically defines at least a portion of the spatial form of theend product. The following parameters are described for the purpose ofdemonstrating some of the potential design parameters of certainembodiments of a method of the present invention.

Layer Thickness

One design parameter can be the thickness of the micro-machined layersof the stack lamination mold. According to certain exemplary embodimentsof the present invention, to achieve high-aspect ratios, multiplemicro-machined foils or layers can be stacked in succession and bondedtogether. In certain exemplary embodiments of the present invention, thelayer thickness can have a dimensional role in creating the desiredshape in the third dimension. FIG. 5A is a top view of an exemplarystack lamination mold 5000. FIGS. 5B-5E are exemplary alternativecross-sectional views of exemplary stack lamination mold 5000 taken atsection lines 5-5 of FIG. 5A. As shown in FIG. 5B and FIG. 5D,respectively, stacks 5010 and 5020 utilize relatively thick layers. Asshown in FIG. 5C and FIG. 5E, respectively, stacks 5030 and 5040 utilizerelatively thinner layers in succession to smooth out resolution alongthe z-axis. Specific layers can have multiple functions that can beachieved through their thickness or other incorporated featuresdescribed herein.

Cross-Sectional Shape of Layer

One design parameter can be the cross sectional shape of a given layerin the mold. Through the use of etching and/or deposition techniques,many cross sectional shapes can be obtained. FIG. 6 is an unassembledcross-sectional view of an alternative exemplary stack lamination mold5000 taken at section lines 5-5 of FIG. 5A. Each of exemplary layers6010, 6020, 6030, and 6040 of FIG. 6 define an exemplary through-feature6012, 6022, 6032, 6042, respectively, each having a different shape,orientation, and/or configuration. These through-features 6012, 6022,6032, 6042 are bordered by one or more “sidewalls” 6014, 6024, 6034, and6044, respectively, as they are commonly referred to in the field oflithographic micro-machining.

Etching disciplines that can be utilized for a layer of the mold can bebroadly categorized as isotropic (non-linear) or anisotropic (linear),depending on the shape of the remaining sidewalls. Isotropic oftenrefers to those techniques that produce one or more radial or hourglassed shaped sidewalls, such as those shown in layer 6010. Anisotropictechniques produce one or more sidewalls that are more verticallystraight, such as those shown in layer 6020.

Additionally, the shape of a feature that can be etched through a foilof the mold can be controlled by the depth of etching on each surfaceand/or the configuration of the photo-mask. In the case ofphoto-chemical-machining, a term such as 90/10 etching is typically usedto describe the practice of etching 90% through the foil thickness, fromone side of the foil, and finishing the etching through the remaining10% from the other side, such as shown on layer 6030. Other etch ratioscan be obtained, such as 80/20, 70/30, and/or 65/35, etc., for variousfoils and/or various features on a given foil.

Also, the practice of displacing the positional alignment of featuresfrom the top mask to the bottom mask can be used to alter the sidewallconditions for a layer of the mold, such as shown in layer 6040.

By using these and/or other specific conditions as design parameters,layers can be placed to contribute to the net shape of the 3-dimensionalstructure, and/or provide specific function to that region of thedevice. For example, an hourglass sidewall could be used as a fluidchannel and/or to provide structural features to the device. FIG. 7 is across-sectional view of an alternative exemplary stack lamination moldtaken at section line 5-5 of FIG. 5A. FIG. 7 shows a laminated mold 5000having layers 7010, 7020, 7030, 7040 that define cavity 7060. To achievethis, layers 7010, 7020 are etched anisotropically to have straightsidewalls, while layer 7030 is thicker than the other layers and isetched isotropically to form the complex shaped cross-section shown.

Cross-Sectional Surface Condition of Layer

Another design parameter when creating advanced three-dimensionalstructures can be the cross-sectional surface condition of the layersused to create a laminated mold. As is the case with sidewall shape,surface condition can be used to provide additional function to astructure or a particular region of the structure. FIG. 8 is aperspective view of a generic laminated mold 8000. FIG. 9 is across-section of mold 8000 taken at lines 9-9 of FIG. 8. Any sidewallsurface, top or bottom surface can be created with one or more specificfinish conditions on all layers or on selected layers, such as forexample, forming a relatively rough surface on at least a portion of asidewall 9100 of certain through-features 9200 of layer 9300. As anotherexample, chemical and/or ion etching can be used to produce very smooth,polished surfaces through the use of selected materials and/orprocessing techniques. Similarly, these etching methods can also bemanipulated to produce very rough surfaces.

Secondary techniques, such as electro-plating and/or passive chemicaltreatments can also be applied to micromachined surfaces (such as alayer of the mold) to alter the finish. Certain secondary techniques(for example, lapping or superfinishing) can also be applied tonon-micromachined surfaces, such as the top or bottom surfaces of alayer. In any event, using standard profile measuring techniques,described as “roughness average” (R_(a)) or “arithmetic average” (AA),the following approximate ranges for surface finish (or surfaceconditions) are attainable using micromachining and/or one or moresecondary techniques according to certain embodiments of the presentinvention (units in microns):

50 to any of: 25, 12.5, 6.3, 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050,0.025,

25 to any of: 12.5, 6.3, 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025,

12.5 to any of: 6.3, 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025,

6.3 to any of: 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025,

3.2 to any of: 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025,

1.6 to any of: 0.80, 0.40, 0.20, 0.10, 0.050, 0.025,

0.80 to any of: 0.40, 0.20, 0.10, 0.050, 0.025,

0.40 to any of: 0.20, 0.10, 0.050, 0.025,

0.20 to any of: 0.10, 0.050, 0.025,

0.10 to any of: 0.050, 0.025,

0.050 to any of: 0.025, etc.

Additional Layer Features

Certain exemplary embodiments of the present invention can include layerfeatures that can be created through the use of lithographic etchingand/or deposition. These embodiments can include the size, shape, and/orpositional orientation of features relative to the X- and/or Y-axes of alayer and/or their relationship to features on neighboring layers alongthe Z-axis of the assembled laminated mold. These parameters can definecertain geometric aspects of the structure. For example, FIG. 10A is atop view of a layer 10010 having a pattern of repeating features (aredundant array of shapes), and FIG. 10B is a top view of a layer 10020having a variety of differently shaped features (a non-redundantcollection of shapes). Although not shown, a layer can have bothredundant and non-redundant features. The terms “redundant” and/or“non-redundant” can refer to either positive or negative features.

Thus, these parameters also can define the shapes and/or spatial formsof features, the number of features in a given area, secondarystructures and/or spaces incorporated on or around a feature, and/or thespaces between features. The control of spacing between features canprovide additional functionality and, for instance, allow integration ofdevices with micro-electronics. For example, conductive micro featurescould be arrayed (redundantly or non-redundantly) to align accuratelywith application specific integrated circuits (ASIC) to controlfeatures. Also, features could be arrayed for applications wherenon-linear spacing between features could enhance device functionality.For example, filtration elements could be arrayed in such a way as tomatch the flow and pressure profile of a fluid passing over or through afiltration media. The spacing of the filtration elements could bearrayed to compensate for the non-linear movement of the fluid.

Cavity Definition Using Lithography

A cavity formed in accordance with certain exemplary embodiments of thepresent invention can assume a shape and/or spatial form that includesone or more predetermined “protruding undercuts”. Imaginarily rotatingthe X-Y plane about its origin to any particular fixed orientation, acavity is defined as having a “protruding undercut” when a first sectionof the cavity taken perpendicular to the Z-axis (i.e., parallel to theX-Y plane) has a predetermined dimension in the X- and/or Y-directiongreater than the corresponding dimension in the X- and/or Y-direction ofa second section of the cavity taken perpendicular to the Z-axis, thesecond section further along in the direction of eventual demolding of acast part relative to the mold (assuming the demolding operationinvolves pulling the cast part free from the mold). That is, theX-dimension of the first section is intentionally greater than theX-dimension of the second section by a predetermined amount, or theY-dimension of the first section is intentionally greater than theY-dimension of the second section by a predetermined amount, or both. Instill other words, for the purposes of this patent application, the termprotruding undercut has a directional component to its definition.

FIG. 11 is a top view of an exemplary stacked laminated mold 11000. FIG.12 is a cross-sectional view of a mold 11000 taken at section lines12-12 of FIG. 11, and showing the layers 12010-12060 of mold 11000 thatcooperatively define a cavity having protruding undercuts 12022 and12042. Direction A is the relative direction in which a part cast usingmold 11000 will be demolded, and/or pulled away, from mold 11000. FIG.12 also shows that certain layers 12020, 12040 of mold 11000 have beenformed by controlled depth etching. As shown in FIG. 12, mold 11000defines an internal mold surface 12070, which is defined in part byprotruding undercuts 12022 and 12042. FIG. 13 is a side view of a castpart 13000 formed using mold 11000. As shown in FIG. 13, cast part 13000defines an external part periphery or surface 13100, which is defined inpart by 3-dimensional micro-features 13400 and 13600 that substantiallyspatially invertedly replicate protruding undercuts 12022 and 12042.

To make layers for certain embodiments of a laminated mold of thepresent invention, such as layers 2010 of FIG. 2, a photo-sensitiveresist material coating (not shown) can be applied to one or more of themajor surfaces (i.e., either of the relatively large planar “top” or“bottom” surfaces) of a micro-machining blank. After the blank has beenprovided with a photo-resist material coating on its surfaces, “masktools” or “negatives” or “negative masks”, containing a negative imageof the desired pattern of openings and registration features to beetched in the blank, can be applied in alignment with each other and inintimate contact with the surfaces of the blank (photo-resist materialsare also available for positive patterns). The mask tools or negativescan be made from glass, which has a relatively low thermal expansioncoefficient. Materials other than glass can be used provided that suchmaterials transmit radiation such as ultraviolet light and have areasonably low coefficient of thermal expansion, or are utilized in acarefully thermally-controlled environment. The mask tools can beconfigured to provide an opening of any desired shape and furtherconfigured to provide substantially any desired pattern of openings.

The resulting sandwich of two negative masks aligned in registration andflanking both surfaces of the blank then can be exposed to radiation,typically in the form of ultraviolet light projected on both surfacesthrough the negative masks, to expose the photo-resist coatings to theradiation. Typically, the photo-resist that is exposed to theultraviolet light is sensitized while the photo-resist that is notexposed is not sensitized because the light is blocked by each negativemasks' features. The negative masks then can be removed and a developersolution can be applied to the surfaces of the blank to develop theexposed (sensitized) photo-resist material.

Once the photo-resist is developed, the blanks can be micro-machinedusing one or more of the techniques described herein. For example, whenusing photo-chemical-machining, an etching solution can react with andremove the layer material not covered by the photo-resist to form theprecision openings in the layer. Once etching or machining is complete,the remaining unsensitized photo-resist can be removed using a chemicalstripping solution.

Sub-Cavities on Layers

Cavities can include sub-cavities, which can be engineered andincorporated into the molding and casting scheme using several methods.FIG. 14 is a top view of a laminated mold 14000. FIG. 15 is across-sectional view of mold 14000 taken at section lines 15-15 of FIG.14, and showing the sub-cavities 15010 within layer 15030 of mold 14000.Note that because layer 15030 is sandwiched between layers 15020 and15040, sub-cavities 15010 can be considered “sandwiched”, becausesub-cavities are at least partially bounded by a ceiling layer (e.g.,15020) and a floor layer (e.g., 15040). Note that, although not shown, asub-cavity can extend to one or more outer edges of its layer, therebyforming, for example, a sandwiched channel, vent, sprew, etc. FIG. 16 isa perspective view of cast part 16000 formed using mold 14000, andhaving protrusions 16010 that reflectively (invertedly) replicatesandwiched sub-cavities 15010.

Because cast part can very accurately reflect the geometries ofsub-cavities, such sub-cavities can be used to produce secondaryfeatures that can be incorporated with a desired structure. Examples ofsecondary features include fluid channels passing through or betweenfeatures, protrusions such as fixation members (similar to Velcro-typehooks), reservoirs, and/or abrasive surfaces. Moreover, a secondaryfeature can have a wall which can have predetermined surface finish, asdescribed herein.

There are a number of methods for producing sub-cavities in a laminatedmold. For example, in the field of photo-chemical-machining, thepractice of partially etching features to a specified depth is commonlyreferred to as “controlled depth etching” or CDE. CDE features can beincorporated around the periphery of an etched feature, such as athrough-diameter. Because the CDE feature is partially etched on, forexample, the top surface of the layer, it can become a closed cavitywhen an additional layer is placed on top.

Another method could be to fully etch the sub-cavity feature through thethickness of the layer. A cavity then can be created when theetched-through feature is sandwiched between layers without thefeatures, such as is shown in FIG. 15.

Combinations of micro-machining techniques can be used to createsub-cavities. For example, photo-chemical-machining (PCM) can be used tocreate the etched-through feature in the layer, while ion etching couldbe applied as a secondary process to produce the sub-cavities. Bycombined etching techniques, the sub-cavities can be etched with muchfiner detail than that of PCM.

Micro-Structures, Features, and Arrays on Non-Planar Surfaces

Certain exemplary embodiments of the present invention can allow theproduction of complex three-dimensional micro-devices on contouredsurfaces through the use of a flexible cavity mold insert.

One activity of such a process can be the creation of a planar laminatedmold (stack lamination), which can define the surface or 3-dimensionalstructures. A second mold (derived mold) can be produced from thelamination using a flexible molding material such as silicone RTV. Thederived mold can be produced having a thin backing or membrane layer,which can act as a substrate for the 3-dimensional surface or features.The membrane then can be mechanically attached to the contoured surfaceof a mold insert, which can define the casting's final shape with theincorporated 3-dimensional features or surface.

As an example, FIG. 17 is a top view of a planar laminated mold 17010having an array of openings 17020. FIG. 18 is a top view of a flexiblecasting or mold insert 18010 molded using laminated mold 17010. Flexiblemold insert 18010 has an array of appendages 18020 corresponding to thearray of openings 17020, and a backing layer 18030 of a controlledpredetermined thickness.

FIG. 19 is a top view of a mold fixture 19010 having an outer diameter19020 and an inner diameter 19030. Placed around a cylinder or mandrel19040 within mold fixture 19010 is flexible mold insert 18010, defininga pour region 19050.

Upon filling pour region 19050, a casting is formed that defines acylindrical tube having a pattern of cavities accessible from its innerdiameter and corresponding to and formed by the array of appendages18020 of flexible mold insert 18010.

As another example, FIG. 20 is a top view of a planar laminated mold20010 having an array of openings 20020. FIG. 21 is a top view of aflexible casting or mold insert 21010 molded using laminated mold 20010.Flexible mold insert 21010 has an array of appendages 21020corresponding to the array of openings 20020, and a backing layer 21030of a controlled predetermined thickness.

FIG. 22 is a top view of a mold fixture 22010 having an outer diameter22020 and an inner diameter 22030. Placed around the inside diameter22030 within mold fixture 22010 is flexible mold insert 21010, defininga pour region 22050.

Upon filling pour region 22050, a casting is formed that defines acylindrical tube having a pattern of cavities accessible from its outerdiameter and corresponding to and formed by the array of appendages21020 of flexible mold insert 21010.

Through these and related approaches, the 3-dimensional structure orsurface can be built-up at the planar stage, and can be compensated forany distortions caused by forming the membrane to the contoured surface.The fabrication of the laminated mold can use specific or combinedmicro-machining techniques for producing the layers that define theaspect-ratio and 3-dimensional geometry. Micro-surfaces and/orstructures can be transferred to many contours and/or shapes. Forexample, micro-patterns can be transferred to the inside and/or outsidediameter of cylinders or tubes. Specific examples demonstrating thecapabilities of this method are provided later in this document.

Cavity Inserts

The term mold insert is used herein to describe a micro-machined patternthat is used for molding and/or fabrication of a cast micro-device,part, and/or item. The laminated or derived mold described in thisdocument also can be considered a mold insert. Cavity inserts aredescribed here as a subset of a mold insert. Cavity inserts are objectsand/or assemblies that can be placed within a cavity section of a moldbut that do not take up the entire cavity space, and that providefurther features to a 3-dimensional mold.

As an example, FIG. 23 is a perspective view of a laminated mold 23010having an array of cylindrical cavities 23020, each extending from topto bottom of mold 23010. FIG. 24 is a close-up perspective view of asingle cylindrical cavity 23020 of mold 23010. Suspended and extendingwithin cavity 23020 are a number of cavity inserts 23030. FIG. 25 is aperspective view of a cast part 25010 having numerous cavities 25020formed by cavity inserts 23030.

A cavity insert can also be produced using certain embodiments of thepresent invention. This is further explained later in the section onnon-planar molds. An insert can be a portion of a mold in the sense thatthe insert will be removed from the cast product to leave a space havinga predetermined shape within the product. An insert alternatively canbecome part of a final molded product. For instance, if it is desirableto have a composite end product, then a process can be engineered toleave an insert in place in the final molded product.

As an example of a cavity insert, a 3-dimensional mold insert can beproduced using one or more embodiments of the present invention, theinsert having an array of cavities that are through-diameters. The castpart derived from this mold can reverse the cavities of the mold assolid diameters having the shape, size and height defined by the mold.To further enhance functionality, cavity inserts can be added to themold before the final casting is produced. In this case, the cavityinsert can be a wire formed in the shape of a spring. The spring canhave the physical dimensions required to fit within a cavity opening ofthe mold, and can be held in position with a secondary fixture scheme.The spring-shaped cavity insert can be removed from the cast part afterthe final casting process is completed. Thus, the cavity section of themold can define the solid shape of the casting while the cavity insertcan form a channel through the solid body in the shape and width of theinsert (the spring). The cavity can serve as, for example, a reservoirand/or a fluid flow restrictor.

The examples given above demonstrate the basic principle of a cavityinsert. Additional design and fabrication advances can be realized byusing this method to create cavity inserts. For example,photo-chemical-machining can be used to create a mold that has largercavity openings, while reactive-ion-etching can be used to create finerfeatures on a cavity insert.

Fabricating the Laminated Mold

Certain exemplary embodiments of the present invention can involve thefabrication of a laminated mold which is used directly and/or as anintermediate mold in one or more subsequent casting and/or moldingprocesses.

FIG. 26 is a block diagram illustrating various devices formed during anexemplary method 26000 for fabricating a laminated mold havingmicro-machined layers that can be patterned and/or etched, and stackedto create a 3-dimensional mold. The laminated mold can be produced as anegative or positive replication of the desired finished casting. Forthe purpose of creating a laminated mold, any of three elements can beimplemented:

-   -   1) creating a lithographic mask 26010 defining the features of        each unique layer,    -   2) using lithographic micro-machining techniques and/or        micro-machining techniques to produce patterned layers 26020,        and/or    -   3) aligning, stacking, and/or laminating the patterned layers        into a stack 26030 in order to achieve the desired 3-dimensional        cavity shape, aspect ratios, and/or mold parameters desired for        a laminated mold 26040.        Lithographic Techniques

Using lithography as a basis for layer fabrication, parts and/orfeatures can be designed as diameters, squares, rectangles, hexagons,and/or any other shape and/or combination of shapes. The combinations ofany number of shapes can result in non-redundant design arrays (i.e.patterns in which not all shapes, sizes, and/or spacings are identical,as shown in FIG. 10). Lithographic features can represent solid orthrough aspects of the final part. Such feature designs can be usefulfor fabricating micro-structures, surfaces, and/or any other structurethat can employ a redundant and/or non-redundant design for certainmicro-structural aspects. Large area, dense arrays can be producedthrough the lithographic process, thereby enabling creation of deviceswith sub-features or the production of multiple devices in a batchformat.

Lithography can also allow the creation of very accurate featuretolerances since those features can be derived from a potentiallyhigh-resolution photographic mask. The tolerance accuracy can includeline-width resolution and/or positional accuracy of the plotted featuresover the desired area. In certain embodiments, such tolerance accuracycan enable micro-scale fabrication and/or accurate integration ofcreated micro-mechanical devices with microelectronics.

Photographic masks can assist with achieving high accuracy when chemicalor ion-etched, or deposition-processed layers are being used to form alaminated mold through stack lamination. Because dimensional changes canoccur during the final casting process in a mold, compensation factorscan be engineered at the photo-mask stage, which can be transferred intothe mold design and fabrication. These compensation factors can helpachieve needed accuracy and predictability throughout the molding andcasting process.

Photographic masks can have a wide range of potential feature sizes andpositional accuracies. For example, when using an IGI Maskwrite 800photoplotter, an active plotting area of 22.8×31.5 inches, minimumfeature size of 5 microns, and positional accuracy of +−1 micron withina 15×15 inch area is possible. Using higher resolution lithographicsystems for mask generation, such as those employed for electron beamlithography, feature sizes as small as 0.25 microns are achievable, withpositional tolerances similar to the Maskwrite plotter, within an areaof 6×6 inches.

Layer Machining and Material Options

Another aspect to fabricating the laminated mold can be the particulartechnique or techniques used to machine or mill-out the features orpatterns from the layer material. In certain embodiments, combininglithographic imaging and micro-machining techniques can improve thedesign and fabrication of high-aspect-ratio, 3-dimensional structures.Some of the micro machining techniques that can be used to fabricatelayers for a laminated mold include photo-etching, laser machining,reactive ion etching, electroplating, vapor deposition, bulkmicro-machining, surface micro-machining, and/or conventional machining.

In certain exemplary embodiments, a laminated mold need only embody themechanical features (e.g., size, shape, thickness, etc.) of the finalcasting. That is, it does not have to embody the specific functionalproperties (i.e. density, conductivity) that are desired to fulfill theapplication of the final casting. This means that any suitabletechniques or materials can be used to produce the layers of the mold.

Thus, there can be a wide variety of material and fabrication options,which can allow for a wide variety of engineered features of a layer,laminated mold, and/or derived mold. For instance, althoughphoto-chemical machining can be limited to metallic foils, by usinglaser machining or reactive ion etching, the choice of materials canbecome greatly expanded. With regard to laser machining, Resonetics,Inc. of Nashua, N.H. commercially provides laser machining services andsystems. For laser machining, a very wide range of materials can beprocessed using UV and infra-red laser sources. These materials includeceramics, metals, plastics, polymers, and/or inorganics. Lasermicro-machining processes also can extend the limits of chemicalmachining with regards to feature size and/or accuracy. With little orno restriction on feature geometry, sizes on the order of 2 microns canbe achievable using laser machining.

When a wide variety of materials are available for making the laminatedmold, process-compatibility issues can be resolved when choosing thematerial from which to create the mold. An example of this would be tomatch the thermal properties of casting materials with those of thelaminated mold, in instances where elevated temperatures are needed inthe casting or molding process. Also the de-molding properties of themold and/or casting material can be relevant to the survival of themold. This, for example, might lead one to laser-machine the layers froma material such as Teflon, instead of a metal. The laser machiningprocess could be compatible with the Teflon and the Teflon could havegreater de-molding capabilities than a metallic stack lamination.

In certain exemplary embodiments of the present invention, only a singlelaminated stack is needed to produce molds or castings. Also, in certainexemplary embodiments of the present invention, molds and/or castingscan be produced without the need for a clean-room processingenvironment.

For certain exemplary embodiments of the present invention, the abilityto create a single laminated mold and then cast the final parts canallow for using much thinner foils or advanced etching methods forproducing the individual layers. Since feature size can be limited bythe thickness of each foil, using thinner foils can allow finer featuresto be etched.

Certain exemplary embodiments of the present invention can combinevarious micro-machining techniques to create layers that have veryspecific functional features that can be placed in predeterminedlocations along the Z-axis of the mold assembly. For example,photo-chemical-machining can be used to provide larger features and highresolution ion-etching for finer features.

Various methods, as described above, can be used to produce layers for alaminated mold. The following examples are given to demonstratedimensional feature resolution, positional accuracy, and/or featureaccuracy of the layers.

Ion Etching:

when using a Commonwealth Scientific Millitron 8000 etching system, forexample, a uniform etch area of 18 inches by 18 inches is achievable.Feature widths from 0.5 microns and above are attainable, depending onthe lithographic masks and imaging techniques used. A feature, forexample a 5 micron wide slot, etched to a depth of 10 microns can beetched to a tolerance of +−1.25 microns in width, and +−0.1 microns indepth. The positional tolerance of features would be the same as thoseproduced on the lithographic masks.

Photo-Chemical-Machining:

when using an Attotech XL 547 etching system, for example, a uniformetch area of 20 inches by 25 inches is achievable. Etchedthrough-feature widths from 20 microns and above are attainable, withsolid features widths of 15 microns and above also being attainable. Afeature, for example a 30 micron diameter etched through 25 microns ofcopper, can be etched to a tolerance of +−2.5 microns or 10% of the foilthickness. The positional tolerance of such features would be the sameas those produced on the lithographic masks.

Laser Micromachining:

when using a PIVOTAL laser micromachining system, for example, a uniformmachining area of 3 inches by 3 inches is achievable. Machinedthrough-feature sizes from 5 microns and above are attainable. Afeature, for example a 5 micron wide slit machined through 25 microns ofstainless steel, can be machined to a tolerance of +−1 micron.Positional tolerance of +−3 microns is achievable over the 3 inch by 3inch area.

Electro-Forming:

depending on the size limitations of the photographic masks used forthis process, electro-forming over areas as large as 60 inches by 60inches is attainable. Electro-formed layers having thickness of 2microns to 100 microns is achievable. A feature, for example a 5 micronwide slit, 15 microns deep, can be formed to a tolerance of +−1 micron.Positional tolerance of features would be the same as those produced onthe lithographic masks.

Layer Assembly and Lamination

As described above, in certain exemplary embodiments of the presentinvention, layers can be designed and produced so that feature shape andplacement from layer to layer define the desired geometry along the X-,Y-, and/or Z-axes of a mold. The total number (and thickness) of layersin the assembly can define the overall height and aspect ratio of thefeature. A feature can be either the solid shape or the space betweengiven structural components.

What follows are several exemplary methods of bonding the layerstogether to form the laminated mold. One exemplary method used to bondlayers together is a metal-to-metal brazing technique. This techniquecan provide a durable mold that can survive high volume productioncasting and/or can provide efficient release properties from thecastings. Prior to assembly, the layers can have 0.00003 inches of aeutectic braze alloy deposited on the top and bottom surfaces of thelayers, using standard electro-plating techniques. An example of a brazematerial is CuSil™, which is comprised of copper and silver, with thepercentage of each being variable for specific applications. CuSil™ canbe designed specifically to lower the temperatures needed to flow thealloy during the brazing process.

One of the potential concerns during the laminating process is tomaintain accurate registration of the assembly layers, and/or controlthe movement of the layers and the bonding fixture when brought to theelevated temperatures needed to flow the braze material. Several methodscan be used to achieve this registration and/or control. The first caninvolve the practice of having two or more alignment features on thelayers. FIG. 27 is a perspective view of a plurality of exemplary layers27000. As illustrated in FIG. 27, one such alignment feature can be adiameter 27010, and the other alignment feature can be an elongated slot27020. The slot and the diameter can be positioned on each layer onehundred eighty degrees opposed, for example, and can be parallel inorientation with the grain and/or perpendicular to the plane of thelayer material.

FIG. 28 is a perspective view of an exemplary laminating fixture 28000,which can be fabricated from graphite, for example, and can have twographite diameter pins 28010 that can be fixed to the lamination fixtureat the same distance apart as the diameter 27010 and slot 27020 on theetched layers 27000. The layers can be placed over the pins 28010 sothat each layer is orientated accurately to the layer below, using theslot and diameter to align each layer. Alternatively, two or morediameters can be provided on the layers 27000, each of which correspondsto a pin of laminating fixture 28000.

During the brazing process, the layered assembly can be heated in ahydrogen atmosphere to a temperature of 825 degrees Celsius, which cancause the CuSil™ braze to flow. As the temperatures elevate, the layersand the fixture material can expand. The slotted alignment feature 27020can allow the fixture 28000 material to expand or move at a dissimilarrate than the layers, by the presence of the elongated slot on the layer27000. The slot 27020 can be greater in length than the diameter of pin28010 in the fixture. The additional length of the slot can bedetermined by the different coefficient for expansion between thegraphite and the assembly layers.

Other methods for maintaining the layer alignment during a heatedbonding process can include fabricating the bonding fixture from thesame material as the assembly layers, which can thus limit thedissimilar movement of the layers and fixture. The alignment and bondingfixture can also be made so that the alignment pins fit nearly perfectlyto alignment features on the layers, but the pins in the fixture areallowed to float while being held perpendicular to the face of thealignment fixture.

In order to minimize positional errors when bonding layers (stackingerrors), tolerances on certain features can be controlled. Referring toFIG. 27, the positional accuracy of features 27010 and 27020 can becontrolled by the photographic masks used to produce the layers(exemplary tolerances for masks are provided in the section titled“Lithographic Techniques”, above). The geometric size and tolerance offeatures 27010 and 27020 can be governed by the layer thickness and/ormicromachining method used to produce them (exemplary tolerances forvarious micromachining techniques are provided in the section titled“Layer Machining and Material Options”, above).

When producing a laminated mold, numerous factors can be an influence onthe overall tolerances of the features of the mold and/or the casting.For example, when using a stacking fixture, any of the laminatingfixture's surface flatness, the laminating fixture's perpendicularity,and the laminating fixture's parallelism can be an influence. Also, thedimensional tolerance of the alignment feature(s) of a layer and/or thepositional tolerance of that feature(s) can be an influence. Forexample, if an alignment pin, protrusion, or other “male” feature willengage a corresponding hole, indentation, or “female” feature to assistin aligning two or more layers, the dimensional tolerance and/orvocational tolerance of male and/or female feature can be an influenceon the overall tolerances.

For example, referring to FIG. 28, bonding fixture 28000 can includealignment pins 28010 fitted into the top surface of fixture 28000. In aparticular experiment, through the use of a surface grinding process,followed by a planetary lapping and polishing process, the sides and topsurface of bonding fixture 28000 were parallel and perpendicular to atolerance of +−2 microns, with the top surface finish being opticallyflat to +−one half the wavelength of visible light (400 to 700nanometers), or about 200 to 350 nanometers. The positional accuracy ofthe alignment pins and the machined diameters through fixture 28000 was+−5 microns, and the pins were perpendicular to the surface of thefixture to +−2 microns, measured at a pin height of 2 to 5 millimeters.The surface of the described fixture measured 6×6 inches, and wasproduced using an SIP 5000 Swiss jig boring milling center. Hardenedsteel alignment pins, having a diameter of 0.092 inches, were preciselyground to a tolerance of +−1.25 microns using a standard grindingoperation.

The process of laminating the layers can include placing the processedlayers over the alignment pins until the desired number of layers havebeen assembled. The assembled layers and fixture then can be placed in abrazing furnace with uniform weight applied to the top of the fixture.The furnace temperature can be raised to a temperature of 825 degreesCelsius, in a hydrogen atmosphere (a vacuum atmosphere has also beenshown to work) for 45 minutes. This temperature can be sufficient toallow the braze material to uniformly flow and connect the layerstogether at all contact points. The fixture then can be cooled in thehydrogen atmosphere for 2 hours and removed for disassembly. Thegraphite pins can be removed, freeing the bonded structure from thelamination fixture.

The brazed lamination now can be ready for the final process step, whichcan be to coat the entire assembly with a hard nickel surface. Thenickel coating can be applied to the laminated assembly usingelectro-plating techniques, which can deposits 0.00001 inches of nickel.The nickel-plated surface can act as an interface material that canenhance the release and durability properties of the assembled mold.

Another exemplary method that can be used to bond layers can make use ofa thermo-cured epoxy rather than metal-to-metal brazing. Prior toassembly, the layers can be coated with an epoxy, MAGNA-TAC® model E645,diluted 22:1 with acetone. The thinned epoxy can be applied to the topand bottom surfaces of the layers using a standard atomizing spray gun.The layers can be spray coated in such a way that the coverage of theepoxy will bond the layers without filling the micro-machined features.A dot coverage of 50% has shown to work. The parameters for dilution andcoverage can be provided by the epoxy manufacture, such as the BeaconChemical Company.

The layers then can be assembled to a bonding fixture using, forexample, the same technique described in the braze process. Theassembled fixture then can be placed in a heated platen press, such as aCarver model #4122. The assembled layers and fixture can be compressedto 40 pounds per square inch and held at a temperature of 350 degrees F.for 3 hours, and allowed to cool to room temperature under constantpressure. The assembly then can be removed from the fixture using, forexample, the same technique used for the brazed assembly.

In certain embodiments, the technique described in the second examplecan be considerably less expensive and time consuming than that used forthe first. Using the epoxy process, savings can be realized due to thecost of the plating and the additional requirement imposed by thehydrogen braze process compared to epoxy stack laminating. The masterderived from the first example can provide more efficient de-moldingproperties and also can survive a greater number of castings than theepoxy bonded mold. The epoxy-bonded mold can demonstrate a costeffective alternative to brazing and can be used for prototyping or whensmaller production quantities are required.

Casting and Molding Process

Exemplary embodiments of the present invention can involve the creationof a high-resolution casting mold, having high-aspect-ratio, as well as3-dimensional features and shapes. A precision stack lamination,comprised of micro-machined layers, can be used as a laminated mold. Thelaminated mold can be used to produce advanced micro-devices andstructures (a.k.a., “micro-electro-mechanical structures” and “MEMS”)and/or can be used to create second (or greater) generation derivedmolds.

The following paragraphs describe the casting process in terms of thematerials, fixtures, and/or methods that can be used to producesecond-generation molds and final castings.

Mold Duplication and Replication

For certain exemplary embodiments of the present invention, the processoptions for producing molds and cast parts can be numerable. Forexample, molds can be made as negative 4010 or positive 4020replications of the desired cast part as shown in FIG. 4. If the mold ismade as a positive, a second-generation mold can be created. If the moldis made as a negative, the final part can be cast directly from themold.

For certain exemplary embodiments of the present invention, the processused to create the layers for the laminated mold can be a determiningfactor. For example, some production situations can require a second-(oreven third) generation derived version of the laminated mold.

In certain situations, process parameters can be greatly enhanced bycombining molding and casting materials having certain predeterminedvalues for physical properties such as durometer, elasticity, etc. Forexample, if the cast part is extremely rigid, with poor releaseproperties, a second-generation consumable mold can be used to createthe final casting. Further specific examples of this practice, and howthey relate to 3-dimensional micro-fabrication are described later inthis document.

Feature size and positional accuracy for molds and produced parts can becompensated for at the layer production stage of the process. Forexample, known material properties such as thermal expansion orshrinkage can be accurately accounted for due to, for example, theaccuracy levels of the photographic masks and/or laser machining used toproduce mold layers. Feature resolution, using various mold making andcasting materials, can be accurately replicated for features having asize of 1 micron and greater. Surface finishes have also been reproducedand accurately replicated. For example, layers have been used to form alaminated mold which was used to produce a derived silicone RTV mold.The surface finish of a 0.0015 inch thick stainless steel layer(specified finish as 8-10 micro inches RA max) and a 0.002 inch thickcopper layer (specified finish as 8-20 micro inches RA max) were easilyidentified on the molded surfaces of the derived RTV mold. The surfaceswere observed at 400× magnification using a Nikon MM11 measuring scope.The same surface finishes were also easily identified when cast partswere produced from the derived mold using a casting alloy CERROBASE™.Very smooth surface finishes, such as those found on glass, have alsobeen reproduced in molds and castings.

Materials for Molds and Castings

For certain exemplary embodiments of the present invention, there can behundreds, if not thousands of material options for mold making andcasting. Described below are some potential considerations regarding theselection of mold and casting materials that can meet the requirementsof, for instance, 3-dimensional MEMS.

To insure the accuracy and repeatability of certain cast micro-devices,the casting material can have the capability to resolve the fine3-dimensional feature geometries of the laminated mold. Typicaldimensions of MEMS can range from microns to millimeters. Otherstructures having micro features can have much larger dimensions.

For certain embodiments, the mold's cavity geometry can influence therelease properties between the mold and the casting, thereby potentiallyimplicating the flexibility (and/or measured durometer) of the materialsused. Other material compatibility issues also can be considered whenusing a casting process.

Certain exemplary embodiments of a process of the present invention havebeen developed in order to enable the production of 3-dimensionalmicro-structures from a wide range of materials, tailored to specificapplications. The ability to use various materials for molds andcastings can greatly expand the product possibilities using thistechnique.

One material that has been successfully used for creating castings froma laminated mold is an elastomeric product, referred to generally as RTVsilicone rubber, although other materials could also be successfuldepending on process or product requirements. A wide range ofsilicone-based materials designed for various casting applications arecommercially available through the Dow Corning Corporation of Midland,Mich. For example, the Silastic® brand products have proven successful,possibly because of their resolution capability, releasecharacteristics, flexibility, durability, and/or the fact that they workin a wide range of process temperatures.

Although other types of silicone rubber products could be used, each ofthe Dow Corning Silastic® brand products that have been used consists oftwo components; a liquid silicone rubber and a catalyst or curing agent.Of the Dow Corning Silastic® brand products, there are two basic curingtypes: condensation, and addition cure. The two types can allow for arange of variations in material viscosities and cure times. The threeprimary products used in the earliest tests are Silastic® J RTV SiliconeRubber, Silastic® M RTV Silicone Rubber, and Silastic® S RTV SiliconeRubber. Product specifications are provided in several of the examplesat the end of this document.

The Dow Corning Silastic® products used thus far have similarspecifications regarding shrinkage, which increases from nil up to 0.3percent if the silicone casting is vulcanized. Vulcanization can beaccomplished by heating the silicone to a specific elevated temperature(above the casting temperature) for a period of 2 hours. Vulcanizing canbe particularly useful when the casting is to be used as a regeneratedmold, and will be subjected to multiple castings.

In addition to RTV silicone rubber, urethanes and other materials alsohave properties that can be desirable for laminated molds, derivedmolds, and/or castings, depending on the specific requirement. Forexample, when producing certain 3-dimensional micro-structures withextreme aspect ratios, very fine features, or extreme under-cuts,de-molding can be difficult. In certain situations, the rigidity of themold also can be relevant, especially in certain cases where moldfeatures have high-aspect ratios. For example, the practice ofsacrificing or dissolving laminated second or third generation molds canbe used when castings require very rigid molds, and/or where thede-molding of castings becomes impossible.

There are several families of materials that can be used for producinglaminated molds, derived molds, and/or final cast devices including, forexample:

-   -   Acrylics: such as, for example, PMMA acrylic powder, resins,        and/or composites, as well as methacrylates such as butyl,        lauryl, stearyl, isobutyl, hydroxethyl, hydroxpropyl, glycidyl        and/or ethyl, etc.    -   Plastic polymerics: such as, for example, ABS, acetal, acrylic,        alkyd, flourothermoplastic, liquid crystal polymer, styrene        acrylonitrile, polybutylene terephthalate, thermoplastic        elastomer, polyketone, polypropylene, polyethylene, polystyrene,        PVC, polyester, polyurethane, thermoplastic rubber, and/or        polyamide, etc.    -   Thermo-set plastics: such as, for example, phenolic, vinyl        ester, urea, and/or amelamine, etc.    -   Rubber: such as, for example, elastomer, natural rubber, nitrile        rubber, silicone rubber, acrylic rubber, neoprene, butyl rubber,        flurosilicone, TFE, SBR, and/or styrene butadiene, etc.    -   Ceramics: such as, for example, silicon carbide, alumina,        silicon carbide, zirconium oxide, and/or fused silica, calcium        sulfate, luminescent optical ceramics, bio-ceramics, and/or        plaster, etc.    -   Alloys: such as, for example, aluminum, copper, bronze, brass,        cadmium, chromium, gold, iron, lead, palladium, silver,        sterling, stainless, zinc platinum, titanium, magnesium,        anatomy, bismuth, nickel, and/or tin, etc.    -   Wax: such as, for example, injection wax, and/or plastic        injection wax, etc.

There can be many material options within these groups that can beutilized when employing certain embodiments of the present invention.For example, in certain embodiments, metals and metal alloys can beprimarily used as structural materials of final devices, but also canadd to function. Exemplary functional properties of metals and/or alloyscan include conductivity, magnetism, and/or shape memory.

Polymers also can be used as structural and/or functional materials formicro-devices. Exemplary functional properties can include elasticity,optical, bio-compatibility, and/or chemical resistivity, to name a few.Materials having dual (or more) functionality, often referred to asengineered “smart” materials, could be incorporated into a final moldedproduct or a mold. Additional functionality could utilize electrostatic,mechanical, thermal, fluidic, acoustic, magnetic, dynamic, and/orpiezo-electric properties. Ceramics materials also can be used forapplications where specialty requirements may be needed, such as certainhigh-temperature environments. Depending on the material that is chosen,there can be many alternative methods to solidify the casting material.The term “solidify” includes, but is not limited to, methods such ascuring, vulcanizing, heat-treating, and/or chemically treating, etc.

Mold Fixtures, Planar and Contoured

For certain exemplary embodiments of the present invention, there can bea wide range of engineering options available when designing a castingmold. The casting process and geometry of the final product candetermine certain details and features of the mold. Options can beavailable for filling and/or venting a mold, and/or for releasing thecasting from the mold.

Two basic approaches have been used for demonstrating the certainexemplary methods for mold design and fabrication. These approaches canbe categorized as using a single-piece open-face mold or a two-partclosed mold.

In certain exemplary embodiments of the present invention, each of themold types can include inserting, aligning, and assembling the laminatedmold (or duplicate copy) in a fixture. The fixture can serve severalpurposes, including bounding and/or defining the area in which to pourthe casting material, capturing the casting material during the curingprocess, allowing the escape of air and/or off-gases while the castingmaterial is degassed, and/or enabling mechanical integration with thecasting apparatus.

The fixture can be configured in such a way that all sides surroundingthe mold insert are equal and common, in order to, for example, equalizeand limit the effects of thermal or mechanical stresses put on the moldduring the casting process. The mold fixture also can accommodate thede-molding of the casting.

Certain exemplary embodiments of this method can provide the ability tomold 3-dimensional structures and surfaces on contoured surfaces. Thebasic technique is described earlier in this document in the designparameter section. One element of the technique can be a flexible moldinsert that can be fixed to a contoured surface as shown in FIGS. 19 and22. The mold insert can be made with a membrane or backing thicknessthat can allow for integration with various fixture schemes that candefine the contoured shape.

For non-planar molds, the contour of the mold fixture can be produced bystandard machining methods such as milling, grinding, and/or CNCmachining, etc. The flexible mold insert can be attached to the surfaceof the mold using any of several methods. One such method is to epoxybond the flexible insert to the fixture using an epoxy that can beapplied with a uniform thickness, which can be thin enough toaccommodate the mold design. Other parameters that can be consideredwhen choosing the material to fix a membrane to a fixture includedurability, material compatibility, and/or temperature compatibility,etc. A detailed description of a non-planar mold is given as an examplefurther on.

Casting and Molding Processes

Various techniques can be used for injecting or filling cavity moldswith casting materials, including injection molding, centrifugalcasting, and/or vibration filling. An objective in any of thesetechniques can be to fill the cavity with the casting material in such away that all of the air is forced out of the mold before the castmaterial has solidified. The method used for filling the cavity mold candepend on the geometry of the casting, the casting material, and/or therelease properties of the mold and/or the cast part.

As has been described earlier, an open face mold, using flexible RTVrubber has been found to work effectively. In certain embodiments, anopen face mold can eliminate the need for having carefully designedentrance sprue and venting ports. The open face mold can be configuredto create an intermediate structure that can have a controlled backingthickness which can serve any of several purposes: 1) it can be an opencavity section in the casting mold which can serve as an entrance pointin which to fill the mold; 2) it can serve as a degassing port for theair evacuation during the vacuum casting process; 3) it can create abacking to which the cast part or parts can be attached and/or which canbe grasped to assist in de-molding the casting from the flexible mold.

In casting processes in which the casting material is heated, the moldtemperature and the cooling of the casting can be carefully controlled.For example, when casting a lead casting alloy such as CERROBASE, thealloy can be held at a temperature of 285 degrees F., while the moldmaterial can be preheated 25-30 degrees higher (310-315 degrees F.). Themolten alloy can be poured and held at or above the melting point untilit is placed in the vacuum environment. The mold then can be placed in avacuum bell jar, and held in an atmosphere of 28 inches of mercury for3-4 minutes. This can remove any air pockets from the molten metalbefore the alloy begins to solidify. As soon as the air has beenevacuated, the mold can be immediately quenched or submersed in coldwater to rapidly cool the molten metal. This can help minimize shrinkageof the cast metal.

In certain exemplary embodiments of the present invention, no vent holesor slots are provided in the mold, and instead, air can be evacuatedfrom the mold prior to injection. In certain exemplary embodiments ofthe present invention, temperature variation and its effect on themicro-structure can be addressed via enhanced heating and coolingcontrols in or around the mold. In certain exemplary embodiments of thepresent invention, heat can be eliminated from the curing process byreplacing the molding materials with photo-curing materials.

Some of the methods that can be used for micro-molding and castinginclude micro-injection molding, powder injection molding, metalinjection molding, photo molding, hot embossing, micro-transfer molding,jet molding, pressure casting, vacuum casting, and/or spin casting, etc.Any of these methods can make use of a laminated or derived moldproduced using this method.

De-Molding and Finish Machining

A controlled backing thickness can be incorporated into the casting tocreate an intermediate structure. One purpose of the intermediate can beto create a rigid substrate or backing, that allows the casting to begrasped for removal from the mold without distorting the casting. Thethickness of the backing can be inversely related to the geometry of thepattern or features being cast. For example, fine grid patterns canrequire a thicker backing while coarse patterns can have a thinnerbacking. The backing can be designed to have a shape and thickness thatcan be used to efficiently grasp and/or pull the cast part from themold.

Following de-molding, the intermediate can be machined to remove thebacking from the casting. Because the thickness of the backing can beclosely controlled, the backing can be removed from the cast structureby using various precision machining processes. These processes caninclude wire and electrode EDM (electrode discharge machining), surfacegrinding, lapping, and/or fly cutting etc.

In instances where extremely fine, fragile patterns have been cast, adissolvable filler or potting material can be poured and cured in thecast structure prior to the removal of the backing from the grid. Thefiller can be used to stabilize the casting features and eliminatepossible damage caused by the machining process. The filler can beremoved after machining-off the backing. A machinable wax has been foundto be effective for filling, machining, and dissolving from the casting.

In some part designs, de-molding the casting from the mold might not bepossible, due to extreme draft angles or extremely fine features. Inthese cases, the mold can remain intact with the cast part or can besacrificed by dissolving the mold from casting.

EXAMPLES

A wide range of three-dimensional micro-devices can be fabricatedthrough the use of one or more embodiments of various fabricationprocesses of the present invention, as demonstrated in some of thefollowing examples.

Example 1 Sub-Millimeter Feedhorn Array

This example demonstrates fabrication of an array of complex3-dimensional cavity features having high aspect ratio. This examplemakes use of a second-generation derived mold for producing the finalpart, which is an array of sub-millimeter feedhorns. A feedhorn is atype of antenna that can be used to transmit or receive electromagneticsignals in the microwave and millimeter-wave portion of the spectrum. Athigher frequencies (shorter wavelengths) the dimensions can become verysmall (millimeters and sub-millimeter) and fabrication can becomedifficult.

Using certain exemplary embodiments of the present invention, a singlehorn, an array of hundreds or thousands of identical horns, and/or anarray of hundreds or thousands of different horns can be fabricated.

FIG. 29 is a top view of stack lamination mold 29000 that defines anarray of cavities 29010 for fabricating feedhorns. FIG. 30 is across-section of a cavity 29010 taken along section lines 30-30 of FIG.29. As shown, cavity 29010 is corrugated, having alternating cavityslots 30010 separated by mold ridges 30020 of decreasing dimensions,that can be held to close tolerances.

In an exemplary embodiment, an array of feedhorns contains one thousandtwenty identical corrugated feedhorns, each designed to operate at 500GHz, and the overall dimensions of the feed horn array are 98millimeters wide by 91 millimeters high by 7.6 millimeters deep. Thefabrication of this exemplary array can begin with the creation of alaminated mold, comprised of micro-machined layers, and assembled into aprecision stack lamination.

Step 1: Creating the laminated mold: The laminated mold in this examplewas made of 100 layers of 0.003″ thick beryllium copper (BeCu) sheetsthat were chemically etched and then laminated together using an epoxybonding process. Infinite Graphics, Inc. of Minneapolis, Minn. wascontracted to produce the photo-masks needed for etching the layers. Themasks were configured with one thousand twenty diameters having acenter-to-center spacing of 2.5 millimeters. An IGI Lazerwrite photoplotter was used to create the masks, which were plotted on silverhalite emulsion film. The plotter resolution accuracy was certified to0.5 micrometers and pattern positional accuracy of plus or minus 0.40micrometers per lineal inch. The layers were designed so that horndiameters were different from layer to layer, so that when the layerswere assembled, the layers achieved the desired cross-section taper,slot, and ridge features shown in simplified form in FIG. 30. A total of100 layers were used to create a stacked assembly 7.6 millimeters thick.The layers were processed by Tech Etch, Inc. of Plymouth, Mass., usingstandard photo-etching techniques and were etched in such a way that thecross-sectional shape of the etched walls for each layer areperpendicular to the top and bottom surfaces of the layer (commonlyreferred to as straight sidewalls).

In this example, the method chosen to bond the etched layers togetherused a thermo-cured epoxy (MAGNA-TAC model E645), using the process andfixturing described earlier in the section on layer assembly andlamination. The assembled fixture was then placed in a 12 inch×12 inchheated platen press, Carver model No. 4122. The fixture was compressedto 40 pounds per square inch and held at a temperature of 350 degrees F.for 3 hours, then allowed to cool to room temperature under constantpressure. The assembly was then removed from the fixture and thealignment pins removed, leaving the bonded stack lamination. Thelaminated mold (stack lamination) was then used to produce the finalcasting mold.

Step 2: Creating the casting mold: The second step of the process wasthe assembly of the final casting mold, which used the precision stacklamination made during step 1 as a laminated mold. The casting moldcreated was a negative version of the lamination, as shown inperspective view for a single feed horn 31000 in FIG. 31. Also shown isa feedhorn ridge 31010 that can correspond to a cavity slot 30010, and afeedhorn base 31020.

For this example, Silastic® J RTV Silicone Rubber was used to make thefinal casting mold. This product was chosen because it is flexibleenough to allow easy release from the laminated mold without damagingthe undercut slots and rings inside the feedhorns, and because of itshigh-resolution capability. Described below are the productspecifications.

Silastic ® J: Durometer Hardness: 56 Shore A points Tensile Strength,psi: 900 Linear Coefficient of 6.2 × 10⁻⁴ Thermal Expansion: Cure Timeat 25 C.: 24 hours

The Silastic® J Silicone RTV was prepared in accordance with themanufacturer's recommendations. This included mixing the silicone andthe curing agent and evacuating air (degassing) from the material priorto filling the mold-making fixture. At the time the example wasprepared, the most effective way of degassing the Silicone prior tofilling the mold fixture was to mix the two parts of the Silicone andplace them in a bell jar and evacuate the air using a dual stage vacuumpump. The material was pumped down to an atmosphere of 28 inches ofmercury and held for 5 minutes beyond the break point of the material.The Silicone was then ready to pour into the mold fixture.

As shown in the side view of FIG. 32, an open-face fixture 32000 wasprepared, the fixture having a precision-machined aluminum ring 32010,precision ground glass plate 32030, rubber gaskets 32040, 32050 and thelaminated mold 32060. The base 32020 of the fixture was thickplexiglass. On top of the plexiglass base was a glass substrate 32030.Rubber gasket 32040 separated the glass base and the glass substrate. Anadditional rubber gasket 32050 was placed on the top surface of theglass substrate 32030 and the laminated mold 32060 was placed on the topgasket. The rubber gaskets were used to prevent unwanted flashing ofmaterial during casting. A precision-machined aluminum ring 32010 wasplaced over the laminated mold subassembly and interfaced with the lowerrubber gasket 32040.

Generally, the height of the ring and dimensions of the above pieces candepend upon the dimensions of the specific structure to be cast. Thering portion 32010 of the fixture assembly served several purposes,including bounding and defining the area in which to pour mold material,capturing the material during the curing process, and providing an airescape while the mold material was degassed using vacuum. The fixturewas configured in a way that all sides surrounding the laminated mold32060 were equal and common, in order to equalize and limit the effectsof thermal or mechanical stresses put on the lamination from the moldmaterial.

An open-face mold was used for this example. The mold insert and moldingfixture were assembled and filled with the silicone RTV, then the airwas evacuated again using a bell jar and vacuum pump in an atmosphere of28 inches of mercury. After allowing sufficient time for the air to beremoved from the silicone, the mold was then heat-cured by placing it ina furnace heated to and held at a constant temperature of 70 degrees F.for 16 hours prior to separating the laminated mold from the derived RTVmold. The molding fixture was then prepared for disassembly, taking careto remove the laminated mold from the RTV mold without damaging thelamination, since the lamination can be used multiple times to createadditional RTV molds.

The resulting RTV mold was a negative version of the entire feedhornarray consisting of an array of one thousand twenty negative feedhorns,similar to the simplified single horn 31010 shown in perspective view inFIG. 31.

Step 3: Casting the feedhorn array: In this example, the cast feedhornarrays were made of a silver loaded epoxy, which is electricallyconductive. In certain exemplary embodiments of the present invention,binders and/or metallic (or other) powders can be combined and/orengineered to satisfy specific application and/or processspecifications. The conductive epoxy chosen for this example providedthe electrical conductivity needed to integrate the feedhorn array withan electronic infrared detector array.

The conductive epoxy was purchased from the company BONDLINE™ of SanJose, Calif., which designs and manufactures engineered epoxies usingpowdered metals. Certain of its composite metal epoxies can be cured atroom temperature, have high shear strength, low coefficient of thermalexpansion, and viscosities suited for high-resolution casting.

Exemplary embodiments of the present invention can utilize varioustechniques for injecting or filling cavity molds with casting materials.In this example, a pressure casting method was used.

The BONDLINE™ epoxy was supplied fully mixed and loaded with the silvermetallic powder, in a semi-frozen state. The loaded epoxy was firstnormalized to room temperature and then pre-heated per themanufacturer's specification. In the pre-heated state the epoxy wasuncured and ready to be cast. The uncured epoxy was then poured into theopen-face mold to fill the entire mold cavity. The mold was then placedin a pressurized vessel with an applied pressure of 50 psi using drynitrogen, and held for one hour, which provided sufficient time for theepoxy to cure. The mold was then removed from the pressure vessel andplaced in an oven for 6 hours at 225 degrees F., which fully cured theconductive epoxy.

Step 4. Demolding and finish machining: After the cast epoxy had beencured, it was ready for disassembly and demolding from the castingfixture and mold. The mold material (RTV silicone) was chosen to beflexible enough to allow the cast feedhorn array to be removed from thecasting mold without damaging the undercuts formed by the slots andridges. When done carefully, the mold could be reused several times tomake additional feedhorn arrays.

The backing thickness 31020 of the RTV mold shown in FIG. 31 came intoplay during the de-molding process. The backing was cast thick enough toallow easy grasping to assist with separating the casting mold from thecast piece. In this example, the RTV casting mold was flexible andallowed easy separation without damaging the undercut slots and ringsinside the cast feedhorns.

Depending on the piece being cast, machining, coating, and/or otherfinish work can be desirable after de-molding. In this example, a finalgrinding operation was used on the top surface (pour side of the mold)of the feedhorn array because an open face mold was used. This finalgrinding operation could have been eliminated by using a closed,two-part mold.

Example 2 Individual Feedhorns Produced in a Batch Process

This example makes use of certain exemplary embodiments of the presentinvention to demonstrate the production of sub-millimeter feedhorns in abatch process. The example uses the same part design and fabricationprocess described in example 1, with several modifications detailedbelow.

Process Modifications:

The process detailed in example 1 was used to produce an array of onethousand twenty feedhorns. The first modification to the process was thecasting material used to produce the array. The casting material forthis example was a two-part casting polymer sold through the SynairCorporation of Chattanooga, Tenn. Product model “Mark 15 Por-A-Kast” wasused to cast the feedhorn array and was mixed and prepared per themanufacturer's specifications. The polymer was also cast using thepressure filling method described in example 1.

The next modification was a surface treatment applied to the castpolymer array. A conductive gold surface was deposited onto the polymerarray in order to integrate the feedhorns with the detector electronics.The gold surface was applied in two stages. The first stage was theapplication of 0.5 microns of conduction gold, which was sputter-coatedusing standard vacuum deposition techniques. The first gold surface wasused for a conductive surface to allow a second stage electro-depositionor plating of gold to be applied. The second gold plating was appliedwith a thickness of 2 microns using pure conductive gold.

The final modification was to dice or cut the feedhorns from the castand plated array into individual feedhorns, that were then suitable fordetector integration. A standard dicing saw, used for wafer cutting, wasused to cut the feedhorns from the cast array.

Example 3 Array of 3-Dimensional Micro-Structures

Process steps 1 and 2 described in example 1 were used to produce alarge area array of micro-structures, which are described as negativesof the feedhorn cavities, shown as a single feedhorn in FIG. 31. Thelaminated mold and molding fixture was used to cast the micro-structuresusing Dow Corning's Silastic® M RTV Silicone Rubber. This product waschosen because it is flexible enough to release from the mold insert,without damaging the circular steps in the structure, but has thehardness needed to maintain the microstructures in a standing positionafter being released from the mold. Described below are the productspecifications.

Silastic ® M Durometer Hardness: 59 Shore A points Tensile Strength,psi: 650 Linear Coefficient of 6.2 × 10⁻⁴ Thermal Expansion: Cure Timeat 25 C.: 16 hours

The Silicone RTV was prepared in accordance with the manufacturer'srecommendations, using the process described earlier in example 1, step2. The laminated mold and molding fixture were assembled and filled withthe silicone RTV, using the process described earlier in example 1, step2. The molding fixture was then prepared for disassembly, taking care toseparate the mold insert from the cast silicone array. The resultingcasting was an array consisting of one thousand twenty 3-dimensionalmicro-structures. The shape and dimension of a single structure is shownin simplified form in FIG. 31.

Example #4 Cylindrical Tubing with Micro-Fluidic Channels on the InsideDiameter

Certain exemplary embodiments of the present invention have been used toproduce a 2.5 centimeter length of clear urethane tubing, having3-dimensional micro-fluid channels on the inside diameter of the tubing.The fluidic tubing was produced using a flexible cavity insert with acontrolled backing thickness. The following example demonstrates how thecavity insert can enable the production of three-dimensional features onthe inside and outside diameters of cylindrical tubing.

Step 1: Creating the Mold Insert:

The first step in the process was to fabricate the micro-machined layersused to produce the cavity insert. The cast tubing was 2.5 centimeterslong, having a 3.0 millimeter outside diameter and a 2.0 millimeterinside diameter, with 50 three-dimensional micro-fluidic channels,equally spaced around the interior diameter of the tube. FIG. 33 shows aside view of the tubing 33000, the wall of which defines numerousfluidic channels 33010. Although each fluidic channel could havedifferent dimensions, in this example each channel was 0.075 mm indiameter at the entrance of the channel from the tube, and each channelextended 0.075 mm deep. Each channel tapered to a diameter of 0.050 mm,the taper beginning 0.025 mm from the bottom of each channel.

Photo-chemical machining was used to fabricate the layers for thelaminated mold. FIG. 34 is a top view of a such a laminated mold 34000,which was created using several photo masks, one of which with a similartop view. Mold 34000 includes an array of fluidic channels 34010 In thisparticular experiment, the length of channels 34010 was approximately 25millimeters, and the width of each collection of channels wasapproximately 6.6 millimeters.

FIG. 35 is a cross-section of mold 34000 taken at section lines 35-35 ofFIG. 34. To the cross-sectional shape of channel 34010, a first copperfoil 35010 having a thickness of 0.025 mm, and a second copper foil35020 having a thickness of 0.050 mm, were chemically etched and thenlaminated together using a metal-to-metal brazing process. Each of thelayers used in the laminated mold assembly used a separate photo-mask.The masks used for layer 35020 were configured with a 9.50×0.075 mmrectangular open slot, arrayed redundantly in 50 places, a portion ofwhich are illustrated in FIG. 34. To achieve the desired taper, twomasks were used for layer 35010. The bottom mask was configured with a9.50×0.075 mm rectangular open slot and the top mask was configured witha 9.50×0.050 rectangular open slot, each of the slots were alsoredundantly arrayed in 50 places. The photo-masks were produced to thesame specifications, by the same vendor as those described in example 1,step 1.

The layers were designed so that the slot placement was identical fromlayer to layer, which when assembled, produced the cross-sectional shapefor the channels as shown in FIG. 35. The final thickness of thelamination was specified at 0.083 millimeters, which required one 0.025layer of copper foil, and one 0.050 thick layer of copper foil, leavinga total thickness amount of 0.002 millimeters for braze material on eachside of each etched layer. The layers were photo-etched by the samevendor, and same sidewall condition as those described in example 1,step 1. The method chosen to bond the grid layers together was ametal-to-metal brazing technique described earlier, in detail as one oftwo exemplary methods of bonding layers together (eutectic braze alloy)

Step 2: Creating the Flexible Cavity Insert:

The next step of the process was to create a flexible cavity insert fromthe brazed layered assembly. FIG. 36 is a side view of cavity insert36000, which was produced from the brazed assembly with a backing 36010having a thickness of 0.050 millimeters. The cavity insert 36000 wasproduced using Silastic® S RTV Silicone Rubber as the base material. TheRTV Silicone Rubber was used because of its resolution capability,release properties, dimensional repeatability, and its flexibility toform the insert to a round pin that would be assembled to the finalmolding fixture. The material properties of Silastic® S are shown below.

Silastic ® S Durometer Hardness: 26 Shore A points Tensile Strength,psi: 1000 Linear Coefficient of 6.2 × 10⁻⁴ Thermal Expansion: Cure Timeat 25 C.: 24 hoursThe casting fixture used to create the RTV cavity insert was similar tothat shown in FIG. 32 and is described in detail in the prior examples.A modification was made to the fixture assembly, which was a top thatwas placed over the pour area of the mold fixture. This top was placedand located to close the mold after air evacuation and reduce thebacking thickness 36010 of the RTV insert to a thickness of 0.050millimeters, shown in FIG. 36. The Silastic® S RTV Silicone Rubber usedfor the cavity insert fabrication was prepared in accordance with themanufacturers recommendations, using the process described earlier inexample 1, step 2.

Step 3: Assembling the Molding Fixture:

The final molding fixture was then ready to be assembled. The moldingfixture included a base plate (FIG. 37), the cavity inserts (FIG. 38),and a top plate (FIG. 40). FIG. 37 is a top view of the base plate37000, which was made from a 0.25 inch aluminum plate that was groundflat and machined using standard CNC machining techniques. The base hadsix machined diameters 37010 through the plate. These six diameterswould accept the cavity insert pins described later. The plate also hadmachined diameters through the plate, which would accept dowel pins37020 that were used to align and assemble the top plate and the baseplate, as well as 4 bolt diameters 37030 to hold the top and bottomplates together.

FIG. 38 is a side view of an insert fixture 38000, that includes theflexible cavity insert 36000 attached to a 3 centimeter long, 1.900millimeter diameter steel pin 38010. The pin 38010 was ground to thedesired dimensions using standard machine grinding techniques. The RTVcavity insert 36000 was cut to the proper size before being attached tothe pin. The RTV insert 36000 was attached to outside diameter of thepin 38010 using a controlled layer of two-part epoxy.

FIG. 39 is a side view of several insert fixtures 39000 that have beenattached to a base plate 37000. Each insert 36000 was attached itscorresponding pin 38010 so that the end of pin 38010 could be assembledto a corresponding machined diameter 37010 of base plate 37000 withoutinterference from insert 36000. Once each insert 36000 was attachedaround the diameter of its corresponding pin 38010 and the pin placed inthe corresponding through-diameter of base plate 37010, the pin was heldperpendicular to base plate 37000 and in alignment with a top plate ofthe fixture.

FIG. 40 is a top view of a top plate 40000 of the fixture, which wasalso fabricated of aluminum and machined using CNC techniques. Therewere six 3.0 millimeter diameters 40010 milled through the thickness ofplate 40000, which was 3.0 centimeters thick. Diameters 40010 definedthe cavity areas of the mold that would be filled during the finalcasting process, and aligned to the pins assembled to the base plate.Also incorporated into the top plate were bolt features 40020 and dowelfeatures 40030 needed to align and assemble the top plate 40000 to thebase plate 37000. The thickness of top plate 40000 was specified toslightly exceed the desired length of the final cast tubing, which wascut to its final length after casting. The casting fixture was thenassembled, first by assembling the cavity insert 38000 to the base plate37000, followed by assembling the top plate 40000 to the base usingbolts and dowels. The top view of a representative cavity section for anassembled fixture is shown in FIG. 19.

Step 4: Casting the Fluidic Tubes:

Several fluidic tubes were produced using the assembled casting fixture.A clear urethane was used for the final casting because of itshigh-resolution, low shrink factor, and transparent properties, whichallowed for final inspection of the interior diameter features throughthe clear wall of the tube. The casting material was purchased from theAlumilite Corporation of Kalamazoo, Mich., under the product name WaterClear urethane casting system. The manufacturer described the curedproperties as follows:

Hardness, Shore D: 82 Density (gm/cc) 1.04 Shrinkage (in/in/) maximum0.005 Cure Time (150 degrees F.) 16 hr

The urethane was prepared in accordance with the manufacturer'srecommendations. This included the mixing and evacuation of air(degassing) from the material prior to filling the mold. The mosteffective way found for degassing the urethane prior to filling the moldfixture was to mix parts A and B, place them in a bell jar, and evacuatethe air using a dual stage vacuum pump. The mixture was pumped down toan atmosphere of 28 inches of mercury and held for 15 minutes beyond thebreak point of the material The urethane was then ready to pour into themold fixture.

The assembled mold fixture was heated to 125 degrees F. prior to fillingthe cavities with the urethane. The pre-heating of the mold helped theurethane to flow and fill the cavities of the mold, and aided in thedegassing process. The cavity sections of the mold were then filled withthe urethane, and the air was evacuated again using a bell jar andvacuum pump in an atmosphere of 28 inches of mercury. After allowingsufficient time for the air to be removed from the urethane, the moldwas then removed from the vacuum bell jar and placed in an oven. Themold was heated and held at a constant temperature of 150-180 degrees F.for 16 hours prior to separating the cast tubes from the mold. Themolding fixture was then disassembled and the cast tubes were separatedfrom the cavity inserts. The inserts were first removed from the baseplate of the fixture. The tubes were easily separated from the cavityinsert assembly due to the flexibility and release properties of thesilicone RTV, combined with the hardness of the urethane tubes.

Example #5 Tubing with Micro-Fluidic Channels on the Outside Diameter

Example #4 described the method used for producing cast urethane tubingwith micro-fluidic features on the inside diameter of the tube. Thecurrent example demonstrates how that process can be altered to producetubing with the micro-fluidic channels on the outside diameter of thetubing. This example uses a similar part design and the fabricationprocess described in example 4, with several modifications detailedbelow.

One process modification involved step 3, assembling the moldingfixture. For this step, a modification was made to the fixture designthat enabled the molded features to be similar to that shown in FIGS.20-22. The first modification was in the size of the machined diametersin the base plate and the top plate of the fixture described in example4. The flexible RTV cavity insert that was attached to a pin in example4 was instead attached to the inside diameters of the top fixture plate,similar to that shown in FIG. 22. In order to accommodate the existingRTV cavity insert, the cavity diameters of the top plate were milled toa size of 1.900 millimeters. The RTV cavity insert was then attached tothe milled diameter of the top plate using the same epoxy techniquedescribed in example 4. The base plate of the fixture was also modifiedto accept a 1.0 millimeter diameter pin, and was assembled similar tothe that shown in FIG. 22. The same casting process was used asdescribed in example 4. After following the final casting process, withthe altered molding fixture, the urethane tubes were produced having thesame fluidic channels located on the outside diameter of the cast tube.

Additional Embodiments X-Ray and Gamma-Ray Collimators, Grids, andDetector Arrays

Certain exemplary embodiments of the present invention can providemethods for fabricating grid structures having high-resolution andhigh-aspect ratio, which can be used for radiation collimators, scatterreduction grids, and/or detector array grids. Such devices can be usedin the field of radiography to, for example, enhance image contrast andquality by filtering out and absorbing scattered radiation (sometimesreferred to as “off-axis” radiation and/or “secondary” radiation).

For the purposes of this description, the term “collimator” is usedgenerally to describe what may also be referred to herein as radiationcollimators, x-ray grids, scatter reduction grids, detector array grids,or any other grid used in radiography apparatuses and processes.

Certain collimators fabricated according to one or more exemplaryembodiments of the present invention can be placed between the objectand the image receptor to absorb and reduce the effects of scatteredx-rays. Moreover, in certain exemplary embodiments, such collimators canbe used in a stationary fashion, like those used in SPECT (Single PhotonEmission Computed Tomography) imaging, or can be moved in areciprocating or oscillating motion during the exposure cycle to obscurethe grid lines from the image, as is usually done in x-ray imagingsystems. Grids that are moved are known as Potter-Bucky grids.

X-ray grid configurations can be specified by grid ratio, which can bedefined as the ratio of the height of the grid to the distance betweenthe septa. The density, grid ratio, cell configuration, and/or thicknessof the structure can have a direct impact on the grid's ability toabsorb off-axis radiation and/or on the energy level of the x-rays thatthe grid can block.

Certain exemplary embodiments of the present invention can allow for theuse of various materials, including high-density grid materials. Also,certain exemplary can make use of a production mold, which can bederived from a laminated mold.

Numerous additional aspects can be fabricated according to certainexemplary embodiments of the present invention. For example, thelaminated mold can be produced from a stack lamination or other method,as discussed above. Moreover, X-ray absorbent material, such as lead,lead alloys, dense metallic composites, and/or epoxies loaded with densemetallic powders can be cast into a mold to produce x-ray absorbinggrids. High-temperature ceramic materials also can be cast using aproduction mold.

In addition, the open cells of the ceramic grid structure can be filledwith detector materials that can be accurately registered to acollimator. The molds and grids can be fabricated having high-resolutiongrid geometries that can be made in parallel or focused configurations.The mold can remain assembled to the cast grid to provide structuralintegrity for grids with very fine septal walls, or can be removed usingseveral methods, and produce an air-cell grid structure.

FIG. 41 is a block diagram illustrating an exemplary embodiment of amethod 41000 of the present invention Method 41000 can include thefollowing activities:

-   -   1) creating a lithographic mask 41010 defining the features of        each unique layer,    -   2) using lithographic micro-machining techniques and/or        micro-machining techniques to produce patterned layers 41020,        and    -   3) aligning, stacking, and/or laminating the patterned layers        41030 in order to achieve the desired 3-dimensional cavity        shape, high-aspect ratios, and/or other device features desired        for the laminated mold 41040,    -   4) fabricating a casting mold 41050 derived from the laminated        mold, and/or    -   5) casting x-ray grids (or other parts) 41060 using the derived        casting mold.        The following discussion describes in detail exemplary        activities involved in fabricating certain exemplary embodiments        of a laminated mold, fabricating a derived mold from the        laminated mold, and finally casting a collimator from the        derived mold. Certain variations in the overall process, its        activities, and the resulting collimator are noted throughout.

In certain exemplary embodiments, the final collimator can be customizedas a result of the casting process. For instance, conventionalcollimators have two separated flat major sides that are parallel toeach other, thereby forming a flat, generally planar grid structure.Although certain exemplary embodiments of the present invention includesmethods for forming these collimators, exemplary embodiments of theinvention also can be used to form non-planar collimators.

An exemplary embodiment of a method of the present invention can beginwith the acquisition, purchase, and/or fabrication of a firstcollimator. This first collimator can serve as the master collimatorfrom which one or more molds can be formed. The master collimator can bemade by any means, including stack lamination, but there is nolimitation with respect to how the first or master collimator can bemade. Also, as will be explained in more detail, because the mastercollimator is not necessarily going to be a collimator used inradiography, it is possible to customize this master collimator tofacilitate mold formation.

The mold itself can be fabricated of many materials. When formed of aflexible material, for example, it is possible to use the mold to make anon-planar collimator. The material of the mold can be customizedaccording to cost and performance requirements. In some embodiments, itis possible to make a mold of material that is substantially transparentto radiation transmission. The mold could be left embedded in the finalcast collimator. This particular variation can be applicable when thefinal collimator has very narrow septal walls and the mold is needed toprovide support and definition for the collimator. The mold generallyalso can be reused to form multiple final (or second) collimators toachieve economies of manufacturing scale.

Radiation Opaque Casting Materials for Collimators and Grids

A broad selection of base materials can be used for the fabrication ofparts, such as x-ray collimators and scatter reduction grids. Onepotential characteristic of a grid material is sufficient absorptioncapacity so that it can block selective x-rays or gamma photons fromreaching an image detector. In certain embodiments of the presentinvention, this characteristic can require high density and/or highatomic number (high z) materials. Certain exemplary embodiments of thepresent invention can utilize lead, tungsten, and/or various lead alloysfor grid fabrication, but also can include the practice of loadingvarious binders or alloys with dense powder metals, such as tungsten.The binders can be epoxies, polymers, and/or dense alloys which aredescribed in detail below.

For certain exemplary embodiments of the present invention, lead can beused for casting purposes because of its high density and low meltingpoint, which can allow the molten lead to be poured or injected into amold. In certain situations, however, pure lead can shrink and/or pullaway from molds when it solidifies, which can inhibit the casting offine features. This can be overcome by using lead alloys, made fromhigh-density materials, which can allow the metal alloy to flow at lowertemperatures than pure lead while reducing shrink factors.

A typical chief component in a lead alloy is bismuth, a heavy, coarsecrystalline metal that can expand by 3.3% of its volume when itsolidifies. The presence of bismuth can expand and/or push the alloyinto the fine features of the mold, thus enabling the duplication offine features. The chart below shows the physical properties of purelead and two lead alloys that were used to produce collimators. Thealloys were obtained from Cerro Metal Products Co. of Bellefonte, Pa.Many other alloys exist that can be used to address specific casting andapplication requirements.

MELT DENSITY BASE MATERIAL COMPOSITION POINT (g/cc) Pure Lead Pb 621.7degrees F. 11.35 CERROBASE ™ 55.5% BI, 255 degrees F. 10.44 44.5% PbCERROLOW-117 ™ 44.7% BI, 117 degrees F. 9.16 22.6% Pb, 19.1% In,  8.3%Sn,  5.3% Cd,

The physical properties of lead alloys can be more process-compatiblewhen compared to pure lead, primarily because of the much lower meltingpoint. For example, the low melt point of CERROBASE™ can allow the useof rubber-based molds, which can be helpful when casting fine-featuredpieces. This can be offset in part by a slightly lower density (about8%). The somewhat lower density, can be compensated for, however, bydesigning the grid structure with an increased thickness and/or slightlywider septal walls.

Also, the alloy can be loaded with dense powder metals, such astungsten, gold, and/or tantalum, etc., to increase density. Similarly,epoxy binders can be loaded with a metallic powder such as, for example,powdered tungsten, which has a density of 19.35 grams per cubiccentimeter. In this approach, tungsten particles ranging in size from1-150 microns, can be mixed and distributed into a binder material. Thebinder material can be loaded with the tungsten powder at sufficientamounts needed to achieve densities ranging between 8 and 14 grams percubic centimeter. The tungsten powder is commercially available throughthe Kulite Tungsten Corporation of East Rutherford N.J., in variousparticle sizes, at a current cost of approximately $20-$25 dollars perpound.

The binders and metallic powders can be combined and engineered tosatisfy specific application and process issues. For example, tungstenpowder can be added to various epoxies and used for casting.

The company BONDLINE™ of San Jose, Calif., designs and manufacturesengineered adhesives, such as epoxies, using powdered metals. Suchcomposite metal epoxies can be cured at room temperature, can have highshear strength, low coefficient of thermal expansion, and viscositiesthat can be suited for high-resolution casting. Powdered materialscombined with epoxy can be stronger than lead or lead alloys, but can besomewhat lower in density, having net density ranging from 7-8 grams percubic centimeter. This density range can be acceptable for somecollimator applications. In applications where material density iscritical the practice of loading a lead alloy can be used. For example,tungsten powder can be combined with CERROBASE™ to raise the net densityof the casting material from 10.44 up to 14.0 grams per cubiccentimeter.

Certain exemplary embodiments of the present invention also include thecasting of grid structures from ceramic materials, such as alumina,silicon carbide, zirconium oxide, and/or fused silica. Such ceramic gridstructures can be used to segment radiation imaging detector elements,such as scintillators. The Cotronics Corporation of Brooklyn, N.Y.,manufactures and commercially distributes Rescor™ Cer-Cast ceramics thatcan be cast at room temperature, can have working times of 30-45minutes, can have cure times of 16 hours, and can withstand temperaturesranging from 2300 to 4000 degrees F.

Additional Embodiments Anti-Scatter Grids for Mammography and GeneralRadiography

One or more exemplary embodiments of the present invention can providecellular air cross grids for blocking scattered X-ray radiation inmammography applications. Such cross grids can be interposed between thebreast and the film-screen or digital detector. In some situations, suchcross grids can tend to pass only the primary, information-containingradiation to the film-screen while absorbing secondary and/or scatteredradiation which typically contains no useful information about thebreast being irradiated.

Certain exemplary embodiments of the present invention can providefocused grids. Grids can be made to focus to a line or a point. That is,each wall defining the grid can be placed at a unique angle, so that ifan imaginary plane were extended from each seemingly parallel wall, allsuch planes would converge on a line or a point at a specific distanceabove the grid center—the distance of that point from the grid known asthe grid focal distance. A focused grid can allow the primary radiationfrom the x-ray source to pass through the grid, producing the desiredimage, while the off-axis scattered rays are absorbed by the walls ofthe grid (known as septal walls).

In certain embodiments, the septal walls can be thick enough to absorbthe scattered x-rays, but also can be as thin as possible to optimizethe transmission ratio (i.e., the percentage of open cell area to thetotal grid area including septal walls) and minimize grid artifacts (theshadow pattern of grid lines on the x-ray image) in the radiograph.

The relation of the height of the septal walls to the distance betweenthe walls can be known as the grid ratio. Higher grid ratios can yield ahigher scatter reduction capability, and thus a higher ContrastImprovement Factor (CIF), which can be defined as the ratio of the imagecontrast with and without a grid. A higher grid ratio can require,however, a longer exposure time to obtain the same contrast, thuspotentially exposing the patient to more radiation. This dose penalty,known as the Bucky factor (BF), is given by BF=CIF/Tp, where Tp is thefraction of primary radiation transmitted. Certain exemplary embodimentsof the present invention can provide a grid design that arrives at anoptimal and/or near-optimal combination of these measures.

One or more exemplary embodiments of the present invention can includefine-celled, focused, and/or large area molded cross-grids, which can besturdily formed from a laminated mold formed of laminated layers ofmetal selectively etched by chemical milling or photo-etching techniquesto provide open focused passages through the laminated stack of etchedmetal layers. In certain applications, such molded and/or cast crossgrids can maximize contrast and accuracy of the resulting mammogramswhen produced with a standard radiation dosage.

In certain exemplary embodiments, the laminated mold for the moldedcross grids can be fabricated using adhesive or diffusion bonding tojoin abutting edges of thin partition portions of the laminated abuttinglayers with minimum intrusion of bonding material into the open focusedpassages.

Exemplary embodiments of the present invention can utilize any of a widenumber of different materials to fabricate such molded and/or cast crossgrids. A specific application can result in any of the followingmaterials being most appropriate, depending on, for example, the netdensity and the cell and septa size requirements:

-   -   Lead or lead alloy alone can offer a density of 9-11 grams per        cc;    -   Lead alloy can be loaded with a dense composite (e.g., tungsten,        tantalum, and/or gold, etc.) powder to form a composite having a        density of 12-15 grams per cc;    -   Polymer can be loaded with a dense composite (e.g., lead,        tungsten, tantalum, and/or gold, etc.) powder to form a        composite having a density of 8-9 grams per cc;    -   The cast grid made of lead alloy or any of the above        combinations can be encapsulated in a low density polymer such        that the transmission is minimally affected but scatter is        significantly reduced.

In addition, certain embodiments of the present invention can beemployed to fabricate grids and/or collimators for which the mold can bepre-loaded with dense powder, followed by alloy or polymer.Alternatively, polymer or alloy can be pre-loaded with dense powder theninjected into the mold. In certain embodiments, the casting can beremoved from a flexible mold. In other embodiments, the mold can bedissolved or consumed to de-mold the casting. In certain embodiments, amaster can be removed layer-by-layer from rigid mold. Alternatively, thelost wax approach can be used in which the model is dissolvable wax,dissolvable PMMA, dissolvable polyurethane, dissolvable high-resolutionceramic, and/or some other dissolvable material.

Additional Embodiments Computed Tomography Collimator and Detector Array

Certain exemplary embodiments of the present invention can provide asystem that includes an x-ray source, a scatter collimator, and aradiation detector array having a plurality of reflective scintillators.Such a system can be used for computer-assisted tomography (“CT”).

In certain exemplary embodiments of the present invention, the x-raysource can project a fan-shaped beam, which can be collimated to liewithin an X-Y plane of a Cartesian coordinate system, referred to as the“imaging plane”. The x-ray beam can pass through the object beingimaged, such as a patient. The beam, after being attenuated by theobject, can impinge upon the array of radiation detectors. The intensityof the attenuated beam radiation received at the detector array can bedependent upon the attenuation of the x-ray beam by the object. Eachdetector element of the array can produce a separate electrical signalthat can provide a measurement of the beam attenuation at the detectorlocation. The attenuation measurements from all the detectors can beacquired separately to produce an x-ray transmission profile of theobject.

For certain exemplary embodiments of the present invention, the detectorarray can include a plurality of detector elements, and can beconfigured to attach to the housing. The detector elements can includescintillation elements, or scintillators, which can be coated with alight-retaining material. Moreover, in certain exemplary embodiments,the scintillators can be coated with a dielectric coating to containwithin the scintillators any light events generated in thescintillators. Such coated scintillators can reduce detector elementoutput gain loss, and thereby can extend the operational life of adetector element and/or array, without significantly increasing thecosts of detector elements or detector arrays.

In certain exemplary embodiments of the present invention, the x-raysource and the detector array can be rotated with a gantry within theimaging plane and around the object to be imaged so that the angle atwhich the x-ray beam intersects the object can constantly change. Agroup of x-ray attenuation measurements, i.e., projection data, from thedetector array at one gantry angle can be referred to as a “view”, and a“scan” of the object can comprise a set of views made at differentgantry angles during one revolution of the x-ray source and detector. Inan axial scan, the projection data can be processed to construct animage that corresponds to a two-dimensional slice taken through theobject.

In certain exemplary embodiments of the present invention, images can bereconstructed from a set of projection data according to the “filteredback projection technique”. This process can convert the attenuationmeasurements from a scan into integers called “CT numbers” or“Hounsfield units”, which can be used to control the brightness of acorresponding pixel on a cathode ray tube display.

In certain exemplary embodiments of the present invention, detectorelements can be configured to perform optimally when impinged by x-raystraveling a straight path from the x-ray source to the detectorelements. Particularly, exemplary detector elements can includescintillation crystals that can generate light events when impinged byan x-ray beam. These light events can be output from each detectorelement and can be directed to photoelectrically responsive materials inorder to produce an electrical signal representative of the attenuatedbeam radiation received at the detector element. The light events can beoutput to photomultipliers or photodiodes that can produce individualanalog outputs. Exemplary detector elements can output a strong signalin response to impact by a straight path x-ray beam.

Without a collimator, X-rays can scatter when passing through the objectbeing imaged. Particularly, the object can cause some, but not all,x-rays to deviate from the straight path between the x-ray source andthe detector. Therefore, detector elements can be impinged by x-raybeams at varying angles. System performance can be degraded whendetector elements are impinged by these scattered x-rays. When adetector element is subjected to multiple x-rays at varying angles, thescintillation crystal can generate multiple light events. The lightevents corresponding to the scattered x-rays can generate noise in thescintillation crystal output, and thus can cause artifacts in theresulting image of the object.

To, for example, reduce the effects of scattered x-rays, scattercollimators can be disposed between the object of interest and thedetector array. Such collimators can be constructed of x-ray absorbentmaterial and can be positioned so that scattered x-rays aresubstantially absorbed before impinging upon the detector array. Suchscatter collimators can be properly aligned with both the x-ray sourceand the detector elements so that substantially only straight pathx-rays impinge on the detector elements. Also, such scatter collimatorscan shield from x-ray radiation damage certain detector elements thatcan be sensitive at certain locations, such as the detector elementedges.

Certain exemplary embodiments of a scatter collimator of the presentinvention can include a plurality of substantially parallel attenuatingblades and a plurality of substantially parallel attenuating wireslocated within a housing. In certain exemplary embodiments, theattenuating blades, and thus the openings between adjacent attenuatingblades, can be oriented substantially on a radial line emanating fromthe x-ray source. That is, each blade and opening can be focallyaligned. The blades also can be radially aligned with the x-ray source.That is, each blade can be equidistant from the x-ray source. Scatteredx-rays, that is, x-rays diverted from radial lines, can be attenuated bythe blades. The attenuating wires can be oriented substantiallyperpendicular to the blades. The wires and blades thus can form atwo-dimensional shielding grid for attenuating scattered x-rays andshielding the detector array.

Depending on the embodiment, the scatter collimator can include bladesand wires, open air cells, and/or encapsulated cells. Certain exemplaryembodiments can be fabricated as a true cross grid having septa in bothradial and axial directions. The cross-grid structure can be aligned inthe radial and axial directions or it can be rotated.

Depending on the grid design, it might not be practical and/or possibleto remove the mold from the cast grid because of its shape or size,e.g., if very thin septa or severe undercuts are involved. In suchcases, a material with a low x-ray absorptivity can be used for the moldand the final grid can be left encapsulated within the mold. Materialsused for encapsulation can include, but are not limited to,polyurethanes, acrylics, foam, plastics etc.

Because certain exemplary embodiments of the present invention canutilize photolithography in creating the laminated mold, greatflexibility can be possible in designing the shape of the open cells.Thus, round, square, hexagonal, and/or other shapes can be incorporated.Furthermore, the cells do not all need to be identical (a “redundantpattern”). Instead, they can vary in size, shape, and/or location(“non-redundant” pattern) as desired by the designer. In addition,because of the precision stack lamination of individual layers that canbe employed in fabricating the master, the cell shapes can vary in thethird dimension, potentially resulting in focused, tapered, and/or othershaped sidewalls going through the cell.

Because the cell shape can vary in the third dimension (i.e. goingthrough the cell), the septa wall shape can also vary. For example, thesepta can have straight, tapered, focused, bulging, and/or otherpossible shapes. Furthermore, the septa do not all need to be identical(a “redundant pattern”). Instead, they can vary in cross-sectional shape(“non-redundant” pattern) as desired by the designer.

Certain exemplary embodiments of the present invention can provide acollimator or section of a collimator as a single cast piece, which canbe inherently stronger than either a laminated structure or an assemblyof precisely machined individual pieces. Such a cast collimator can bedesigned to withstand any mechanical damage from the significantg-forces involved in the gantry structure that can rotate as fast as 4revolutions per second. Furthermore, such a cast structure can besubstantially physically stable with respect to the alignment betweencollimator cells and detector elements.

Some exemplary embodiments of the present invention can provide acollimator or section of a collimator as a single cast collimator inwhich cells and/or cell walls can be focused in the radial direction,and/or in which cells and/or cells walls can be accurately aligned inthe axial direction.

Conversely, certain exemplary embodiments of the present invention canprovide a collimator or section of a collimator as a single castcollimator in which cells and/or cell walls can be focused (by stackinglayers having slightly offset openings) in the axial direction, and/orin which cells and/or cells walls can be curved (and focused) in theradial direction.

Exemplary embodiments of the present invention can utilize any of a widenumber of different materials to fabricate the scatter collimator. Aspecific application can result in any of the following materials beingmost appropriate, depending on, for example, the net density and thecell and septa size requirements. Lead or lead alloy alone can offer adensity of 9-11 grams per cc;

-   -   Lead alloy can be loaded with a dense composite (e.g., tungsten,        tantalum, and/or gold, etc.) powder to form a composite having a        density of 12-15 grams per cc;    -   Polymer can be loaded with a dense composite (e.g., lead,        tungsten, tantalum, and/or gold, etc.) powder to form a        composite having a density of 8-9 grams per cc;    -   The cast grid made of lead alloy or any of the above        combinations can be encapsulated in a low density polymer such        that the transmission is minimally affected but scatter is        significantly reduced.

In addition, certain embodiments of the present invention can beemployed to fabricate grids and/or collimators for which the mold can bepre-loaded with dense powder, followed by alloy or polymer.Alternatively, polymer or alloy can be pre-loaded with dense powder theninjected into the mold. In certain embodiments, the casting can beremoved from a flexible mold. In other embodiments, the mold can bedissolved or consumed to de-mold the casting. In certain embodiments, amaster can be removed layer-by-layer from rigid mold. Alternatively, thelost wax approach can be used in which the model is dissolvable wax,dissolvable PMMA, dissolvable polyurethane, dissolvable high-resolutionceramic, and/or some other dissolvable material.

The above description and examples have covered a number of aspects ofcertain exemplary embodiments of the invention including, for example,cell size and shape, different materials and densities, planar andnon-planar orientations, and focused and unfocused collimators.

Additional Embodiments Nuclear Medicine (SPECT) Collimator and DetectorArray

Certain embodiments of the present invention can be used to fabricatestructures useful for nuclear medicine. For example, collimators used innuclear medicine, including pinhole, parallel-hole, diverging, andconverging collimators, can be fabricated according to one or moreexemplary methods of the present invention.

As another example, exemplary methods of the present invention can beused to fabricate high precision, high attenuation collimators withdesign flexibility for hole-format, which can improve the performance ofpixelated gamma detectors.

Certain exemplary embodiments of certain casting techniques of thepresent invention can be applied to the fabrication of other componentsin detector systems. FIG. 47 is an assembly view of components of atypical pixelated gamma camera. Embodiments of certain castingtechniques of the present invention can be used to produce collimator47010, scintillator crystals segmentation structure 47020, and opticalinterface 47030 between scintillator array (not visible) andphoto-multiplier tubes 47040.

In an exemplary embodiment, collimator 47010 can be fabricated fromlead, scintillator crystals segmentation structure 47020 can befabricated from a ceramic, and optical interface 47030 can be fabricatedfrom acrylic.

In certain exemplary embodiments, through the use of a commonfabrication process, two or more of these components can be made to thesame precision and/or positional accuracy. Moreover, two or more ofthese components can be designed to optimize and/or manage seams and/ordead spaces between elements, thereby potentially improving detectorefficiency for a given choice of spatial resolution. For example, in apixelated camera with non-matched detector and collimator, if thedetector's open area fraction (the fraction of the detector surface thatis made up of converter rather than inter-converter gap) is 0.75, andthe collimator's open area fraction (the fraction of the collimatorsurface that is hole rather than septum) is 0.75, the overall open areafraction is approximately (0.75)=0.56. For a similar camera in which thecollimator holes are directly aligned with the pixel converters, theopen area fraction is 0.75, giving a 33% increase in detectionefficiency without reduction in spatial resolution.

Certain embodiments of the present invention can provide parallel holecollimators and/or collimators having non-parallel holes, such as fanbeam, cone beam, and/or slant hole collimators. Because certainembodiments of the present invention use photolithography in creatingthe master, flexibility is possible in designing the shape, spacing,and/or location of the open cells. For example, round, square,hexagonal, or other shapes can be incorporated. In addition, becausecertain embodiments of the present invention use precision stacklamination of individual layers to fabricate a laminated mold, the cellshapes can vary in the third dimension, resulting in focused, tapered,and/or other shaped sidewalls going through the cell. Furthermore, thecells do not all need to be identical (“redundant”). Instead, they canvary in size, shape or location (“non-redundant”) as desired by thedesigner, which in some circumstances can compensate for edge effects.Also, because a flexible mold can be used with certain embodiments ofthe present invention, collimators having non-planar surfaces can befabricated. In some cases, both surfaces are non-planar. However,certain embodiments of the present invention also allow one or moresurfaces to be planar and others non-planar if desired.

Certain embodiments of the present invention can fabricate a collimator,or section of a collimator, as a single cast piece, which can make thecollimator less susceptible to mechanical damage, more structurallystable, and/or allow more accurate alignment of the collimator with thedetector.

Certain embodiments of the present invention can utilize any of a numberof different materials to fabricate a collimator or other component ofan imaging system. A specific application could result in any of thefollowing materials being chosen, depending, in the case of acollimator, on the net density and the cell and septa size requirements:

-   -   Lead or lead alloy alone can offer a density of 9-11 grams per        cc    -   Polymer can be loaded with tungsten powder to form a composite        having a density comparable to lead or lead alloys    -   Polymer can also be combined with other dense powder composites        such as tantalum or gold to yield a density comparable to lead        or lead alloys    -   Polymer can be combined with two or more dense powders to form a        composite having a density comparable to lead or lead alloys    -   Lead alloy can be loaded with tungsten powder to form a        composite having a density of 12-15 grams per cc    -   Lead alloy can be loaded with another dense composites        (tantalum, gold, other) to form a composite having a density of        12-15 grams per cc    -   Lead alloy can be combined with two or more dense powders to        form composites having a density of 12-15 grams per cc (atomic        number and attenuation)    -   The cast grid made of lead alloy or any of the above        combinations can be encapsulated in a low-density material such        that the transmission is minimally affected but scatter is        reduced.

Thus, depending on the specific application, certain embodiments of thepresent invention can create any of a wide range of densities for thecast parts. For example, by adding tungsten (or other very densepowders) to lead alloys, net densities greater than that of lead can beachieved. In certain situations, the use of dense particles can providehigh “z” properties (a measure of radiation absorption). For certainembodiments of the present invention, as radiation absorption improves,finer septa walls can be made, which can increase imaging resolutionand/or efficiency.

In addition, certain embodiments of the present invention can beemployed to fabricate grids and/or collimators for which the mold can bepre-loaded with dense powder, followed by alloy or polymer.Alternatively, polymer or alloy can be pre-loaded with dense powder theninjected into the mold. In certain embodiments, the casting can beremoved from a flexible mold. In other embodiments, the mold can bedissolved or consumed to de-mold the casting. In certain embodiments, amaster can be removed layer-by-layer from rigid mold. Alternatively, thelost wax approach can be used in which the model is dissolvable wax,dissolvable PMMA, dissolvable polyurethane, dissolvable high-resolutionceramic, and/or some other dissolvable material.

With certain embodiments of the present invention, the stack-laminatedmaster does not need to embody the net density of the final grid.Instead, it can have approximately the same mechanical shape and size.Similarly, the final grid can be cast from relatively low cost materialssuch as lead alloys or polymers. Furthermore, these final grids can beloaded with tungsten or other dense powders. As discussed previously,using certain embodiments of the invention, multiple molds can be madefrom a single master and multiple grids can be cast at a time, ifdesired. Such an approach can lead to consistency of dimensions and/orgeometries of the molds and/or grids.

Because of the inherent precision of the lithographic process, certainembodiments of the present invention can prevent and/or minimizeassembly build up error, including error buildup across the surface ofthe grid and/or assembly buildup error as can occur in collimators inwhich each grid is individually assembled from photo-etched layers. Inaddition, process errors can be compensated for in designing thelaminated mold.

Example 6 Lead Collimator for Gamma Camera (Nuclear MedicineApplication)

Step 1: Creating the laminated mold: In this exemplary process, 0.05 mmthick copper foils were chemically etched and then laminated togetherusing a metal-to-metal brazing process, for producing a laminated mold.Photo-masks were configured with a 2.0×2.0 millimeter square open cell,with a 0.170 mm septal wall separating the cells. The cells were arrayedhaving 10 rows and 10 columns, with a 2 mm border around the cell array.Photo-masks were produced to the same specifications, by the same vendoras those described in example 1, step 1.

The layers were designed so that the cell placement was identical fromlayer to layer, which when assembled, produced a parallelcross-sectional shape. FIG. 42A is a top view of an x-ray grid 42000having an array of cells 42002 separated by septal walls 42004. FIG. 42Bis a cross-sectional view of x-ray grid 42000 taken along section lines42-42 of FIG. 42B showing that the placement of cells 42002 can also bedissimilar from layer to layer 42010-42050, so that when assembled,cells 42002 are focused specifically to a point source 42060 at a knowndistance from x-ray grid 42000.

The total number of layers in the stack lamination defined the thicknessof the casting mold and final cast grid. The final thickness of thelamination was specified at 0.118 inches, which required 57 layers ofcopper foil, leaving a total thickness amount of 0.00007 inches betweeneach layer for a braze material. The layers were processed by Tech Etchof Plymouth Mass., using standard photo-etching techniques and wereetched in such a way that the cross-sectional shape of the etched wallswere perpendicular to the top and bottom surfaces of the foil (commonlyreferred to as straight sidewalls).

The method chosen to bond the grid layers together was a metal-to-metalbrazing technique described earlier in detail as one of two exemplarymethods of bonding layers together (eutectic braze alloy). The brazedlamination was then electro-plated with a coating of hard nickel, alsodescribed earlier.

Step 2: Creating a derived mold: An RTV mold was made from the stacklaminated mold from step 1. Silastic® M RTV Silicone Rubber was chosenas the base material for the derived mold. This particular material wasused to demonstrate the resolution capability, release properties,multiple castings, and dimensional repeatability of the derived moldfrom the laminated mold. Silastic M has the hardest durometer of theSilastic® family of mold making materials. The derived mold wasconfigured as an open face mold.

The fixture used to create the derived casting mold is shown in FIG. 32and was comprised of a precision machined aluminum ring 32010, precisionground glass plates 32020 and 32030, rubber gaskets 32040 and 32050, andthe laminated mold 32060. The base of the fixture 32020 was a 5 inchsquare of 1 inch thick plexiglass. On the top surface of the plexiglassbase was a 1″ thick, 3 inch diameter glass substrate 32030. The base andthe glass substrate were separated by a 1/16 inch thick, 4.5 inchdiameter rubber gasket 32040. An additional 3.0 inch rubber gasket 32050was placed on the top surface of the glass substrate 32030. The rubbergaskets helped prevent unwanted flashing of molten material whencasting. The laminated mold 32060 was placed on the top gasket.

The shape and thickness of the glass created the entrance area where thecasting material was poured into the mold. The material formed in thiscavity was referred to as a controlled backing. It served as a releaseaid for the final casting, and could later be removed from the castingin a final machining process. A precision machined aluminum ring 32010having a 4.5 inch outside diameter and a 4 inch inside diameter wasplaced over the master subassembly and interfaced with the lower 4.5inch diameter rubber gasket.

As illustrated in FIG. 32, the height of the ring was configured so thatthe distance from the top surface of the master to the top of the ringwas twice the distance from the base of the fixture to the top of thelaminated mold. The additional height allowed the RTV material to riseup during the degassing process. The ring portion of the fixtureassembly was used to locate the pouring of the mold material into theassembly, captivate the material during the curing process, and providean air escape while the mold material was degassed using vacuum. Thefixture was configured in such a way that all sides surrounding thelaminated mold were equal and common, in order to limit the effects orstresses put on the lamination from the mold material.

The Silastic® M RTV Silicone Rubber used for the mold fabrication wasprepared in accordance with the manufacturer's recommendations, usingthe process described earlier in example 1, step 2.

The laminated mold was characterized, before and after the mold-makingprocess, by measuring the average pitch distance of the cells, theseptal wall widths, overall distance of the open grid area, and thefinished thickness of the part. These dimensions were also measured onthe derived casting mold and compared with the laminated mold before andafter the mold-making process. The following chart lists the dimensionsof the lamination before and after the mold-making and the samedimensions of the derived RTV mold. All dimensions were taken using aNikon MM-11 measuring scope at 200× magnification. These dimensionsdemonstrated the survivability of the master and the dimensionalrepeatability of the mold.

Master Master Lamination Lamination Grid (before mold- RTV Mold (aftermold- Feature making) Silastic ® M making) Septal Wall 0.170 0.161 0.170Width (mm) Cell Width 2.000 × 2.000 2.010 × 2.010 2.000 × 2.000 (mm)Cell Pitch 2.170 × 2.170 2.171 × 2.171 2.170 × 2.170 (mm) Pattern 21.530× 21.530 21.549 × 21.549 21.530 × 21.530 area (mm) Thickness 2.862 2.8332.862 (mm)

Step 3: Casting the final collimator: A fine-featured lead collimatorwas produced from the derived RTV silicone mold described in step 2.FIG. 43 is a side view of an assembly 43000 that includes an open facemold 43010 that was used to produce a casting 43020 from CERROBASE™alloy. Casting 43020 was dimensionally measured and compared to thelaminated mold 43010. The backing 43030 of casting 43020 was 6millimeters in thickness and was removed using a machining process.

Grid Features Master Lamination Cast Collimator Septal Wall Width (mm)0.170 0.165 Cell Width (mm) 2.000 × 2.000 2.005 × 2.005 Cell Pitch (mm)2.170 × 2.170 2.170 × 2.170

The first step of the casting process was to pre-heat the derived RTVmold to a temperature of 275 degrees F., which was 20 degrees above themelting point of the CERROBASE™ alloy. The mold was placed on a heatedaluminum substrate, which maintained the mold at approximately 275degrees F. when it was placed in the vacuum bell jar.

In certain casting procedures, the material can be forced into the moldin a rapid fashion, and cooled and removed quickly. In this case, thecasting process was somewhat slowed in order to fully fill and evacuatethe air from the complex cavity geometry of the mold. The CERROBASE™ wasthen heated in an electric melting pot to a temperature of 400 degreesF., which melted the alloy sufficiently above its melt point to remainmolten during the casting process.

The next step was to pour the molten alloy into the mold, in such a wayas to aid in the displacement of any air in the cavity. This wasaccomplished by tilting the mold at a slight angle and beginning thepour at the lowest point in the cavity section of the mold. It was foundthat if the mold was placed in a flat orientation while pouring themolten alloy, significant amounts of air were trapped, creating problemsin the degassing phase of the process. Instead, once the mold wassufficiently filled with the molten alloy, the mold was slightlyvibrated or tapped in order to expel the largest pockets of air. Themold, on the heated aluminum substrate, was then placed in the vacuumbell jar, pumped down to atmosphere of 25-28 inches of mercury for 2minutes, which was sufficient time to evacuate any remaining airpockets. The mold was then removed from the vacuum bell jar andsubmersed in a quenching tank filled with water cooled to a temperatureof 50 degrees F. The rapid quench produced a fine crystalline grainstructure when the casting material solidified. The casting was thenremoved from the flexible mold by grasping the backing 43030, bymechanical means or by hand, and breaking the casting free of the moldusing an even rotational force, releasing the casting gradually from themold.

The final process step was removing the backing 43030 from the attachedsurface of the grid casting 43020 to the line shown in FIG. 43. Prior toremoving the backing, the grid structure of the final casting 43020 wasfilled or potted with a machineable wax, which provided the structuralintegrity needed to machine the backing without distorting the finewalls of the grid casting. The wax was sold under the product nameMASTER™ Water Soluble Wax by the Kindt-Collins Corporation, ofCleveland, Ohio. The wax was melted at a temperature of 160-180 degreesF., and poured into the open cells of the cast grid. Using the sametechnique described above, the wax potted casting was placed in vacuumbell jar and air evacuated before being cooled. The wax was cooled toroom temperature and was then ready for the machining of the backing.

A conventional surface grinder was used to first rough cut the backingfrom the lead alloy casting. The remaining casting was then placed on alapping machine and lapped on the non-backing side of the casting usinga fine abrasive compound and lapping wheel. The non-backing side of thecasting was lapped first so that the surface was flat and parallel towithin 0.010-0.015 millimeters to the adjacent cast grid cells. Therough-cut backing surface was then lapped using the same abrasive wheeland compound so that it was flat and parallel to within 0.100-0.015millimeters of the non-backing side of the casting. A thickness of 2.750millimeters was targeted as the final casting thickness. Upon completionof the lapping process, the casting was placed in an acid solution,comprised of 5% dilute HCL and water, with mild agitation until the waxwas fully dissolved from the cells of the casting.

In an alternative embodiment, individual castings could also be stacked,aligned, and/or bonded to achieve thicker, higher aspect ratiocollimators. Such collimators, potentially having a thicknesses measuredin centimeters, can be used in nuclear medicine.

Example 7 Non-Planar Collimator

A non-planar collimator can have several applications, such as, forexample, in a CT environment. To create such an example of such acollimator, the following process was followed:

Step 1: Creating a Laminated Mold:

For this example, a laminated mold was designed and fabricated using thesame process and vendors described in Example 1, step 1. The laminatedmold was designed to serve as the basis for a derived non-planar castingmold. The laminated mold was designed and fabricated with outsidedimensions of 73.66 mm×46.66 mm, a 5 mm border around a grid area having52×18 open cell array. The cells were 1 mm×1.980 mm separated by 0.203septal walls.

The layers for the laminated mold were bonded using the same processdescribed in Example 1, step 1 (thermo-cured epoxy). The dimensions ofthe laminated mold were specified to represent a typical collimator forCT x-ray scanning. Silastic® J RTV Silicone Rubber was chosen as a basematerial to create a derived non-planar casting mold because of itsdurometer which allowed it to more easily be formed into a non-planarconfiguration. The laminated mold and fixture was configured as an openface mold.

Step 2: Creating a Derived Non-Planar Mold:

Silastic® J RTV Silicone Rubber was used for the derived moldfabrication and was prepared in accordance with the manufacturersrecommendations, using the process described earlier in example 1, step2. FIG. 44 is a top view of casting assembly 44000. FIG. 45 is a sideview of casting assembly 44000.

The derived RTV mold 44010 was then formed into a non-planarconfiguration as shown in FIG. 45. The surface 44020 of casting fixturebase 44030 defined a 1-meter radius arc to which mold 44010 wasattached. A 1-meter radius was chosen because it is a common distancefrom the x-ray tube to the collimator in a CT scanner. Mold 44010 wasfastened to the convex surface 44020 of casting base 44030 with a hightemperature epoxy adhesive. A pour frame 44040 was placed around castingfixture base 44030. Pour frame 44040 had an open top to allow pouringthe casting material to a desired fill level and to allow evacuating theair from the casting material.

The laminated mold was characterized, before and after producing thederived non-planar mold, by measuring the average pitch distance of thecells, the septal wall widths, overall distance of the open grid area,and the finished thickness of the part. These dimensions were alsomeasured on the derived non-planar mold and compared with the masterbefore and after the mold-making process. The following chart lists thedimensions of the master lamination before and after the mold-making andthe same dimensions of the RTV mold in the planar state and curvedstate. All dimensions are in millimeters and were taken using a NikonMM-11 measuring scope at 200× magnification.

Master Lamination RTV Mold RTV Mold Grid (before mold- (planar) (curved)Features making) Silastic ® J Silastic ® J Septal Wall 0.203 0.183 0.193* Cell Width 1.980 × 1.000 2.000 × 1.020 2.000 × 1.020 Cell Pitch2.183 × 1.203 2.183 × 1.203 2.183 × 1.213 Pattern area 39.091 × 62.35339.111 × 62.373 39.111 × 62.883 Thickness 7.620 7.544 7.544 *measured inthe direction of curvature.

Step 3: Casting a Non-Planar Collimator:

The derived non-planar RTV mold described in step 2, was used to createcastings. Using the derived non-planar mold, the castings were producedfrom CERROBASE™ alloy and were dimensionally measured and compared tothe laminated mold.

Grid Features Master Lamination Cast Collimator Septal Wall Width (mm)0.203 0.197* Cell Width (mm) 1.000 × 1.980 1.006 × 1.986 Cell Pitch (mm)1.203 × 2.183 1.203 × 2.183 *measured in the direction of curvature.

The process used to fill the derived non-planar mold with the castingalloy and the de-molding of the casting was the same process describedin Example 6.

The final process step included the removal of the backing from the gridcasting. A wire EDM (electrode discharge machining) process was found tobe the most effective way to remove the backing from the casting,primarily due to the curved configuration of the casting. The wire EDMprocess used an electrically charged wire to burn or cut through thecasting material, while putting no physical forces on the parts. In thiscase, a fine 0.003 inch molybdenum wire was used to cut the part, at acutting speed of 1 linear inch per minute. This EDM configuration waschosen to limit the amount of recast material left behind on the cutsurface of the part, leaving the finished septal walls with a smoothsurface finish. The casting was fixtured and orientated so that theradial cutting of the backing was held parallel to the curved surface ofthe casting, which was a 1 meter radius.

Example 8 Mammography Scatter Reduction Grid

Another exemplary application of embodiments of the present invention isthe fabrication of a mammography scatter reduction grid. In thisexample, a derived clear urethane mold for a fine-featured focused gridwas made using a photo-etched stack lamination for the master model. Formaking this mold, the master was designed and fabricated using thelamination process detailed in Example 7. A clear urethane castingmaterial was chosen as an example of a cast grid in which the mold wasleft intact with the casting as an integral part of the grid structure.This provided added strength and eliminated the need for a fragile orangled casting to be removed from the mold.

Step 1: Creating a Laminated Mold:

The laminated mold was fabricated from photo-etched layers of copper.The mold was designed to have a 63 mm outside diameter, a 5 mm borderaround the outside of the part, and a focused 53 mm grid area. FIG. 46is a top view of a grid area 46000, which was comprised of hexagonalcells 46010 that were 0.445 mm wide, separated by 0.038 mm septal walls46020. The cells were focused from the center of the grid pattern to afocal point of 60 centimeters, similar to that shown in FIG. 42B. Thegrid was made from 35 layers of 0.050 mm thick stainless steel, whichwhen assembled created a 4:1 grid ratio. Each grid layer utilized aseparate photo-mask in which the cells are arrayed out from the centerof the grid pattern at a slightly larger distance from layer to layer.This created the focused geometry as shown in FIG. 42B. With this cellconfiguration, the final casting produced a hexagonal focused grid witha transmission of about 82%. The photo-masks and etched layers wereproduced using the same vendors and processes described in example 1,step 1.

Step 2: Creating a Derived Urethane Mold:

Urethane mold material was chosen for its high-resolution, low shrinkfactor, and low density. Because of its low density, the urethane issomewhat transparent to the transmission of x-rays. The mold material,properties, and process parameters were as described earlier in example4, step 4.

The fixture used to create the derived urethane casting mold was thesame as that described in Example 6, step 2.

Before assembling the mold fixture, the laminated mold was sprayed witha mold release, Stoner E236. The fixture was assembled as shown in FIG.32 and heated to 125 degrees F. Then it was filled with the Water Clearurethane and processed using the same parameters described in example 4,step 4. The laminated mold was characterized, before and after makingthe derived mold, by measuring the average pitch distance of the cells,the septal wall widths, overall distance of the open grid area, and thefinished thickness of the lamination. These dimensions were alsomeasured on the derived urethane casting mold and compared with thelamination before and after the mold-making process. The following chartlists the dimensions of the lamination before and after the mold-makingand the same dimensions of the urethane mold. All dimensions were inmillimeters and were taken using a Nikon MM-11 measuring scope at 200×magnification.

Master Urethane Master Lamination Casting Lamination Grid (before mold-System (after mold- Features making) Water Clear making) Septal 0.0380.037 0.038 Wall Width Cell Width 0.445 0.446 0.445 (hexagonal)(hexagonal) (hexagonal) Cell Pitch 0.483 0.483 0.483 Pattern 53.000 52.735  53.000  area (mm2) Thickness 1.750 1.729 1.750

Step 3: Casting the Anti-Scatter Grid:

A focused scatter reduction grid was produced by casting a lead alloy,CERROLOW-117™ alloy into the derived urethane mold described in step 2.The backing thickness of the casting was 2 millimeters and was removedusing a surface grinding process.

The first step of the process was to pre-heat the derived urethane moldto a temperature of 137 degrees F., which was 20 degrees above the 117degree melting point of the CERROLOW™ alloy. The mold was placed on aheated aluminum substrate, which maintained the mold to approximately117 degrees F. when it was placed in the vacuum bell jar. The CERROLOW™was then heated in an electric melting pot to a temperature of 120degrees F., which melted the alloy sufficiently above the melt point ofthe material, keeping the material molten during the casting process.The process steps for filling the mold were the same as those describedin Example 6, step 3.

The CERROLOW™ alloy was chosen for casting because of its highresolution capability, low melting point, and relatively high density.The urethane mold was left remaining to provide structural integrity forthe fine lead alloy features. The urethane is also somewhat transparentto x-rays because of its low density (1 g/cm³) compared to the castingalloy.

Example 9 Collimator with Tungsten Loaded Alloy (Variation of Example 6)

Additional collimator samples have been produced using the same processdescribed in Example 6 above, with the exception of the casting alloyand that it was loaded with tungsten powder prior to the castingprocess. The tungsten powder (KMP115) was purchased through the KuliteTungsten Corporation of East Rutherford, N.J. CERROLOW™ alloy was loadedto raise the net density of the alloy from a density of 9.16 grams percubic centimeter to 13 grams per cubic centimeter.

In certain radiological applications, elimination of secondary scatteredradiation, also known as Compton scatter, and shielding can be anobjective. The base density of the CERROLOW™ alloy can be sufficient onits own to absorb the scattered radiation, but the presence of thetungsten particles in the septal walls can increase the density andimprove the scatter reduction performance of the part. The casting wasdimensionally measured and compared to the laminated mold used to createthe derived RTV mold.

Grid Features Master Lamination Cast Collimator Material CopperCERROLOW-117 Plus Tungsten Powder Density (g/cc) 8.96  12.50  SeptalWall Width 0.038 0.036 Cell Width 0.445 0.447 (hexagonal) (hexagonal)Cell Pitch 0.483 0.483 *all dimensions are in millimeters.

Prior to casting, the tungsten powder was loaded or mixed into theCERROLOW™ alloy. The first step was to super-heat the alloy to 2-3 timesits melting point temperature (between 234-351 degrees F.), and tomaintain this temperature. The tungsten powder, having particle sizesranging from 1-15 microns in size, was measured by weight to 50% of thebase alloy weight in a furnace crucible. A resin-based, lead-compatiblesoldering flux was added to the tungsten powder to serve as a wettingagent when combining the powder and the alloy. The resin flux wasobtained from the Indium Corporation of America of Utica N.Y., under thename Indalloy Flux #5RMA.

The flux and the powder were heated to a temperature of 200 degrees F.and mixed together after the flux became liquid. The heated CERROLOW™alloy and the fluxed powder then were combined and mixed using ahigh-shear mixer at a constant temperature of 220 degrees F. The netdensity of the alloy loaded with the powder was measured at 12.5 gramsper cubic centimeter. The loaded alloy was molded into the derived RTVmold, and finished machined using the same process described in Example6.

Example 10 Collimator Structure Cast from a Ceramic (Variation ofExample 7)

This example demonstrates a structure that could be co-aligned with acast collimator. The structure could be filled with detector materials,such as a scintillator, for pixilation purposes. Ceramic was chosen forhigh temperature processing of the scintillator materials, which arenormally crystals.

Additional cast samples have been produced using a castable silicaceramic material using the same mold described in Example 7 above. Theceramic material, Rescor™-750, was obtained from the CotronicsCorporation of Brooklyn, N.Y. The ceramic material was prepared prior tocasting per the manufacturer's instructions. This included mixing theceramic powder with the supplied activator. Per the manufacturer'sinstructions, an additional 2% of activator was used to reduce theviscosity of the mixed casting ceramic, in order to aid in filling thefine cavity features of the mold.

The mold was filled and degassed using a similar process and the samemold and non-planar fixture as Example 7 above, covered with a thinsheet of plastic, and allowed to cure for 16 hours at room temperature.The ceramic casting then was removed from the RTV mold and post cured toa temperature of 1750 degrees F., heated at a rate of 200 degrees F. perhour. Post-curing increased the strength of the cast grid structure. Theceramic casting then was ready for the final grinding and lappingprocess for the removal of the backing.

Additional Fields of Use

Additional fields of use and devices are contemplated for variousembodiments of the invention. Among those additional fields and devicesare:

Automotive Industry

-   -   Technology Areas:        -   Inertial measurement        -   Micro-scale Power generation        -   Pressure measurement        -   Fluid dynamics    -   Representative Devices:        -   accelerometers        -   rate sensors        -   vibration sensors        -   pressure sensors        -   fuel cells        -   fuel processors        -   nozzle technology        -   valves and regulators        -   pumps        -   filters        -   relays        -   actuators        -   heaters

Avionics Industry

-   -   Technology Areas:        -   Inertial measurement        -   RF technology        -   Communications        -   Active structures and surfaces    -   Representative Devices:        -   conformable MEMS (active and passive)        -   micro-satellite components        -   micro-thrusters        -   RF switches        -   antennas        -   phase shifters        -   displays        -   optical switches        -   accelerometers        -   rate sensors        -   vibration sensors        -   pressure sensors        -   fuel cells        -   fuel processors        -   nozzle technology        -   valves and regulators        -   pumps        -   filters        -   relays        -   actuators        -   heaters

Biological and Biotechnology

Technology Areas:

-   -   Micro-fluidics    -   Microbiology    -   DNA assays    -   Chemical testing    -   Chemical processing    -   Lab-on-a-chip    -   Tissue engineering    -   Analytical instrumentation    -   Bio-filtration    -   Test and measurement    -   Bio-computing    -   Biomedical imaging    -   Representative Devices:        -   biosensors        -   bioelectronic components        -   reaction wells        -   microtiterplates        -   pin arrays        -   valves        -   pumps        -   bio-filters        -   tissue scaffolding        -   cell sorting and filtration membranes

Medical (diagnostic and therapeutic)

Technology Areas:

-   -   Imaging    -   Interventional radiography    -   Orthopedic    -   Cardiac and vascular devices    -   Catheter based tools and devices    -   Non-invasive surgical devices    -   Medical tubing    -   Fasteners    -   Surgical cutting tools    -   Representative Devices:        -   airways        -   balloon catheters        -   clips        -   compression bars        -   drainage tubes        -   ear plugs        -   hearing aids        -   electrosurgical hand pieces and tubing        -   feeding devices        -   balloon cuffs        -   wire/fluid coextrusions        -   lumen assemblies        -   infusion sleeves/test chambers        -   introducer tips/flexible sheaths        -   seals/stoppers/valves        -   septums        -   stents        -   shunts        -   membranes        -   electrode arrays        -   ultra-sound transducers        -   infra-red radiation sensors        -   radiopaque targets or markers        -   collimators        -   scatter grids        -   detector arrays

Military

Technology Areas:

-   -   Weapon safeing    -   Arming and fusing    -   Miniature analytical instruments    -   Biomedical sensors    -   Inertial measurement    -   Distributed sensing and control    -   Information technology    -   Representative Devices:        -   MEMS fuse/safe-arm devices        -   ordinance guidance and control devices        -   gyroscopes        -   accelerometers        -   disposable sensors        -   spectrometers        -   active MEMS surfaces (large area)        -   micro-mirror MEMS displays

Telecommunications

-   -   Technology Areas:        -   Optical switches        -   Displays        -   Adaptive optics    -   Representative Devices:        -   micro-relays        -   optical attenuators        -   photonic switches        -   micro-channel plates        -   optical switches        -   displays            Microvalves

Microvalves can be enabling components of many microfluidic systems thatcan be used in many industry segments. Microvalves are generallyclassified as passive or active valves, but can share similar flowcharacteristics through varied orifice geometries. Diaphragm microvalvescan be useful in many fluidic applications. FIG. 48A is a top view of anarray 48010 of generic microdevices 48000. FIG. 48B is a cross sectionof a particular microdevice 48000 in this instance a diaphragmmicrovalve, taken along section lines 48-48 of FIG. 48A, the microvalveincluding diaphragm 48010 and valve seat 48020, as shown in the openposition. FIG. 49 is a cross section of the diaphragm microvalve 48000,again taken along section lines 48-48 of FIG. 48A, the microvalve in theclosed position.

The flow rate through diaphragm microvalve 48000 can be controlled viathe geometric design of the valve seat, which is often referred to asgap resistance. The physical characteristics of the valve seat, incombination with the diaphragm, can affect flow characteristics such asfluid pressure drop, inlet and outlet pressure, flow rate, and/or valveleakage. For example, the length, width, and/or height of the valve seatcan be proportional to the pressure drop across the microvalve'sdiaphragm. Additionally, physical characteristics of the diaphragm caninfluence performance parameters such as fluid flow rate, which canincrease significantly with a decrease in the Young's modulus of thediaphragm material. Valve leakage also can become optimized with adecrease in the Young's modulus of the diaphragm, which can enablehigher deflection forces, further optimizing the valve's overallperformance and/or lifetime.

Typical microvalve features and specifications can include a valve seat:The valve seat, which is sometimes referred to as the valve chamber, canbe defined by its size and the material from which it is made. Using anexemplary embodiment of a method of the present invention, thedimensions of the chamber can be as small as about 10 microns by about10 microns if square, about 10 microns in diameter if round, etc., witha depth in the range of about 5 microns to millimeters or greater. Thus,aspect ratios of 50, 100, or 200:1 can be achieved. The inner walls ofthe chamber can have additional micro features and/or surfaces which caninfluence various parameters, such as flow resistance, Reynolds number,mixing capability, heat exchange fouling factor, thermal and/orelectrical conductivity, etc.

The chamber material can be selected for application specific uses. Asexamples, a ceramic material can be used for high temperature gas flow,or a chemical resistant polymer can be used for chemical uses, and/or abio-compatible polymer can be used for biological uses, to name a few.Valve chambers can be arrayed over an area to create multi-valveconfigurations. Each valve chamber can have complex inlet and outletchannels and/or ports to further optimize functionality and/or provideadditional functionality.

Typical microvalve features and specifications can also include adiaphragm: The diaphragm can be defined by its size, shape, thickness,durometer (Young's modulus), and/or the material from which it is made.Using an exemplary embodiment of a method of the present invention, thedimensions of the diaphragm can be as small as about 25 microns by about25 microns if square, about 25 microns in diameter if round, etc., withthickness of about 1 micron or greater. The surface of one side or bothsides of the diaphragm could have micro features and/or surfaces toinfluence specific parameters, such as diaphragm deflection and/or flowcharacteristics. The diaphragm can be fabricated as a free form devicethat is attached to the valve in a secondary operation, and/or attachedto a substrate. Diaphragms can be arrayed to accurately align to amatching array of valve chambers.

Potential performance parameters can include valve seat and diaphragmmaterial, diaphragm deflection distance, inlet pressure, flow, and/orlifetime.

Micropumps

FIGS. 50 and 51 are cross-sectional views of a particular micro-device48000, in this case a typical simplified micropump, taken along sectionlines 48-48 of FIG. 48A. Micropumps can be an enabling component of manymicrofluidic systems that can be used in many industry segments.Reciprocating diaphragm pumps are a common pump type used inmicro-fluidic systems. Micropump 50000 includes two microvalves 50010and 50020, a pump cavity 50030, valve diaphragms 50040 and 50050, andactuator diaphragm 50060.

At the initial state of pump 50000, the actuation is off, both inlet andoutlet valves 50010 and 50020 are closed, and there is no fluid flowthrough pump 50000. Once actuator diaphragm 50060 is moved upwards, thecavity volume will be expanded causing the inside pressure to decrease,which opens inlet valve 50010 and allows the fluid to flow into and fillpump cavity 50030, as seen in FIG. 50. Then actuator diaphragm 50060moves downward, shrinking pump cavity 50030, which increases thepressure inside cavity 50030. This pressure opens outlet valve 50020 andthe fluid flows out of the pump cavity 50030 as seen in FIG. 51. Byrepeating the above steps, continuous fluid flow can be achieved. Theactuator diaphragm can be driven using any of various drives, includingpneumatic, hydraulic, mechanical, magnetic, electrical, and/orpiezoelectrical, etc. drives.

Typical microvalve features and specifications can include any of thefollowing, each of which are similar to those features andspecifications described herein under Microvalves:

-   -   Valve seats    -   Valve actuators (diaphragm)    -   Cavity chamber    -   Actuator diaphragm

Potential performance parameters can include valve seat, chambermaterial, actuator diaphragm material, valve diaphragm material,deflection distance for actuator, deflection distance for valvediaphragms, inlet pressure, outlet pressure, chamber capacity, flowrate, actuator drive characteristics (pulse width, frequency, and/orpower consumption, etc.), and/or lifetime.

Microwells and Microwell Arrays

Microwells can be an enabling component in many devices used formicro-electronics, micro-mechanics, micro-optics, and/or micro-fluidicsystems. Precise arrays of micro-wells, potentially having hundreds tothousands of wells, can further advance functionality and processcapabilities. Microwell technology can be applied to DNA micro-arrays,protein micro-arrays, drug delivery chips, microwell detectors, gasproportional counters, and/or arterial stents, etc. Fields of use caninclude drug discovery, genetics, proteomics, medical devices, x-raycrystallography, medical imaging, and/or bio-detection, to name a few.

For example, using exemplary embodiments of the present invention,microwells can be engineered in the third (Z) dimension to producecomplex undercuts, pockets, and/or sub-cavities. Wells can also bearrayed over various size areas as redundant or non-redundant arrays.These features can include the dimensional accuracies and/or tolerancesdescribed earlier. Also, a range of surface treatments within the wellstructure are possible that can enhance the functionality of the well.

Examples of Microwell Applications:

DNA Microarrays:

Scientists can rely on DNA microarrays for several purposes,including 1) to determine gene identification, presence, and/or sequencein genotype applications by comparing the DNA on a chip; 2) to assessexpression and/or activity level of genes; and/or 3) to measure levelsof proteins in protein based arrays, which can be similar to DNA arrays.

DNA microarrays can track tens of thousands of reactions in parallel ona single chip or array. Such tracking is possible because each probe (agene or shorter sequence of code) can be deposited in an assignedposition within the cell array. A DNA solution, representing a DNAsample that has been chopped into constituent sequences of code, can bepoured over the entire array (DNA or RNA). If any sequence of the samplematches a sequence of any probe, the two will bind, and non-bindingsequences can be washed away. Because each sequence in the sample oreach probe can be tagged or labeled with a fluorescent, any boundsequences will remain in the cell array and can be detected by ascanner. Once an array has been scanned, a computer program can convertthe raw data into a color-coded readout.

Protein Microarrays:

The design of a protein array is similar to that of a DNA chip. Hundredsto thousand of fluorescently labeled proteins can be placed in specificwells on a chip. The proteins can be deposited on the array via a pin orarray of pins that are designed to draw fluidic material from a well anddeposit it on the inside of the well of the array. The position andconfiguration of the cells on the array, the pins, and the wells arelocated with the accuracy needed to use high-speed pick-and-placerobotics to move and align the chip over the fluidic wells. A bloodsample is applied to the loaded array and scanned for bio-fluorescentreactions using a scanner.

Certain embodiments of the invention enable DNA or Protein microarrayshaving a potentially large number of complex 3-dimensional wells to befabricated using any of a range of materials. For example, structurescan be fabricated that combine two or more types of material in amicrowell or array. Additional functionality and enhancements can bedesigned into a chip having an array of microwells. Wells can beproduced having cavities capable of capturing accurate amounts of fluidsand/or high surface-to-volume ratios. Entrance and/or exitconfigurations can enhance fluid deposition and/or provide visualenhancements to scanners when detecting fluorescence reactions. Veryprecise well locations can enable the use of pick and place roboticswhen translating chips over arrays of fluidic wells. Certain embodimentsof the invention can include highly engineered pins and/or pin arraysthat can be accurately co-aligned to well arrays on chips and/or canhave features capable of efficiently capturing and/or depositing fluidsin the wells.

Arterial Stents:

Stents are small slotted cylindrical metal tubes that can be implantedby surgeons to prevent arterial walls from collapsing after surgery.Typical stents have diameters in the 2 to 4 millimeter range so as tofit inside an artery. After insertion of a stent, a large number ofpatients experience restenosis—a narrowing of the artery—because of thebuild-up of excess cells around the stent as part of the healingprocess. To minimize restenosis, techniques are emerging involving theuse of radioactive elements or controlled-release chemicals that can becontained within the inner or outer walls of the stent.

Certain embodiments of the invention can provide complex 3-dimensionalfeatures that can be designed and fabricated into the inside, outside,and/or through surfaces of tubing or other generally cylindrical and/orcontoured surfaces. Examples 4 and 5 teach such a fabrication techniquefor a 3 mm tube. Certain embodiments of the invention can allow themanufacture of complex 2-dimensional and/or 3-dimensional featuresthrough the wall of a stent. Micro surfaces and features can also beincorporated into the stent design. For example, microwells could beused to contain pharmaceutical materials. The wells could be arrayed inredundant configurations or otherwise. The stent features do not have tobe machined into the stent surface one at a time, but can be appliedessentially simultaneously. From a quality control perspective, featuresformed individually typically must be 100% inspected, whereas featuresproduced in a batch typically do not. Furthermore, a variety ofapplication specific materials (e.g., radio-opaque, biocompatible,biosorbable, biodissolvable, shape-memory) can be employed.

Microwell Detectors:

Microwells and microwell arrays can be used in gas proportional countersof various kinds, such as for example, in x-ray crystallography, incertain astrophysical applications, and/or in medical imaging. One formof microwell detector consists of a cylindrical hole formed in adielectric material and having a cathode surrounding the top opening andanode at the bottom of the well. Other forms can employ a point or pinanode centered in the well. The microwell detector can be filled with agas such as Xenon and a voltage can be applied between the cathode andanode to create a relatively strong electric field. Because of theelectric field, each x-ray striking an atom of the gas can initiate achain reaction resulting in an “avalanche” of hundreds or thousands ofelectrons, thereby producing a signal that can be detected. This isknown as a gas electron multiplier. Individual microwell detectors maybe used to detect the presence and energy level of x-rays, and if arraysof microwell detectors are employed, an image of the x-ray source can beformed. Such arrays can be configured as 2-dimensional and/or3-dimensional arrays.

Certain embodiments of the invention can enable arrays of complex3-dimensional wells to be fabricated and bonded or coupled to otherstructures such as a cathode material and anode material. It is alsopossible to alter the surface condition of the vertical walls of thewells, which can enhance the laminar flow of electrons in the well. Anumber of possible materials can be used to best meet the needs of aparticular application, enhancing parameters such as conductivity,die-electrical constant, and/or density. Certain embodiments of theinvention can further enable the hybridizing of micro-electronics to awell array, in particular because of accurate co-alignment between themicro-electronic feature(s), and/or the structural elements of the well.

Typical Microwell Features, Specifications and Potential PerformanceParameters:

FIG. 52 is a top view of an exemplary microwell array 52000, showingmicrowells 52010, and the X- and Y-axes. Array 52000 is shown asrectangle, but could be produced as a square, circle, or any othershape. Either of the array's dimensions as measured along the X- orY-axes can range from 20 microns to 90 centimeters. Microwells 52010 areshown having circular perimeters, but could also be squares, rectangles,or any other shape. Array 52000 is shown having a redundant array ofwells 52010, but could be produced to have non-redundant wells. Thepositional accuracy of wells 52010 can be accurate to the specificationsdescribed herein for producing lithographic masks. Wells can range insize from 0.5 microns to millimeters, with cross-sectionalconfigurations as described herein.

Using certain embodiments of a method of the present invention, certainmaterials can be used to produce microwell arrays for specific uses. Forexample, a ceramic material can be used for high-temperature gas flow, achemical resistant polymer can be used for chemical uses, and/or abio-compatible polymer can be used for biological uses, to name a few.Specialty composite materials can enhance application specificfunctionality by being conductive, magnetic, flexible, hydrophilic,hydrophobic, piezoelectric, to name a few.

Using an embodiment of a method of the present invention, microwellswith certain 3-dimensional cross-sectional shapes can be produced. FIG.52 is a top view of an exemplary array 52000 of microwells 52010.

FIG. 53 is a cross-sectional view, taken at section lines 52-52 of FIG.52, of an exemplary microwell 53000 having an entrance 53010. Entrance53010 is shown having a tapered angle, which could be angled from 0degrees to nearly 180 degrees. Entrance 53010 is also shown having adifferent surface than well area 53020. Well area 53020 can be square,round, rectangular, or any other shape. Well area 53020 can range insize from 0.5 microns to millimeters in width and can be dimensionallycontrolled in the Z-axis to have aspect ratios of from about 50:1 toabout 100:1. As shown in FIG. 53, microwell 53000 defines microwellsurfaces 53050, 53060, 53070, 53080, 53090, 53100, 53110. As also shownin FIG. 53, a cross-sectional surface 53030 is defined that intersectsmicrowell surfaces 53050, 53060, 53070, 53080, 53090, 53100, 53110. Asfurther shown in FIG. 53, a central area and/or layer-less volume 53040of cross-sectional surface 53030 comprises a majority of cross-sectionalsurface 53030, yet does not include any of microwell surfaces 53050,53060, 53070, 53080, 53090, 53100, 53110, which define a periphery 53120of central area and/or layer-less volume 53040 of microwell 53000.

FIG. 54 is a cross-sectional view, taken at section lines 52-52 of FIG.52, of an alternative exemplary microwell 54000 that defines an entrance54010, a well 54020, and an exit 54030. Microwell 54000 can be used inapplications that require fluids that are conveyed from below or abovethe entrance 54010 and/or exit 54030, and deposited in well 54020. Usingan embodiment of a method of the present invention, microwell 54000 canbe produced so that well 54020 is hydrophilic and entrance 54010 andexit 54030 are hydrophobic to, for example, enable the deposition offluid into well 54020, and discourage the fluid deposition, retention,and/or accumulation on entrance 54010, on exit 54030, and/or on thechip's surface. For uses where microelectronic controls or chips areemployed, the material surrounding and/or defining entrance 54010 and/or54030 can be conductive or non-conductive, as required. Well 54020 canbe dimensioned to accurately contain a pre-determined amount of fluid.

The shape and size of corner feature 54040 can be defined to encouragethe discharge of a fluid material from a fluidic channel on a pin, whena pin is produced using any of certain embodiments of the invention. Forexample, pins can be produced having fluidic channels or undercuts thatare positioned radially at the end of the pin. The undercuts can serveas reservoirs that increase surface area-to-volume ratios and/or holdaccurate amounts of fluids. If the undercuts are designed to berelatively flexible and larger than the opening dimension at feature54040, fluid can be squeezed from the reservoir as the fluid passes bycorner feature 54040. Entrance 54010 can have an angle that promotes thevisibility of a material, such as a fluid, in well 54020. The materialsurrounding and/or defining well 54020 can be fabricated to havemicro-surface features to increase the well's surface area-to-volumeratio.

FIG. 55 is a top view of an exemplary microwell 55000 showing a wellarea 55010 and sub-cavities 55020. FIG. 56 is a cross-sectional view,taken at section lines 56-56 of FIG. 55, of microwell 55000 showing well55010 and sub-cavities 55020. Well 55010 can extend through the materialthat defines it, as shown in FIG. 56, or can be a closed well having asolid floor. Sub-cavities 55020 can be incorporated within a well to,for example, increase an area of the surface(s) bordering the well, avolume, and/or surface area-to-volume ratio of the well. Sub-cavities55020 can be continuous rings as shown in FIG. 55. Alternatively,sub-cavities 55020 can be discrete pockets forming sub-wells within well55010. Sub-cavities 55020 can be positioned on a horizontal floor orsubfloor of well 55010 as shown in FIG. 55, on the vertical walls ofwell 55010, and/or on another surface. Sub-cavities 55020 can havecircular, square, rectangular, and/or any of a variety of othercross-sectional shapes. Sub-cavities 55020 can also be positioned toprovide an enhanced visual perspective of a deposited material fromwhich could be angled from 0 degrees to nearly 180 degrees, such as anapproximately perpendicular angle, so as to enhance scanning performanceor resolution.

Filtration

Filtration can be an important element in many industries includingmedical products, food and beverage, pharmaceutical and biological,dairy, waste water treatment, chemical processing, textile, and/or watertreatment, to name a few. Filters are generally classified in terms ofthe particle size that they can separate. Micro-filtration generallyrefers to separation of particles in the range of approximately 0.01microns through 20 microns. Separation of larger particles thanapproximately 10-20 microns is typically referred to as particleseparation. There are two common forms of filtration, cross-flow anddead-end. In cross-flow separation, a fluid stream runs parallel to amembrane of a filter while in dead-end separation, the filter isperpendicular to the fluid flow. There are a very large number ofdifferent shapes, sizes, and materials used for filtration depending onthe particular application.

Certain embodiments of the invention can be filters suitable formicro-filtration and/or particle filtration applications. Certainembodiments of the invention allow fabrication of complex 2-dimensionaland/or 3-dimensional filters offering redundant or non-redundant poresize, shape, and/or configuration. For example, a circular filter canhave an array of redundant generally circular through-features, eachthrough-feature having a diameter slightly smaller than a targetparticle size. Moreover, the through-feature can have a tapered,countersunk, and/or undercut entrance, thereby better trapping anytarget particle that encounters the through-feature. Further, thecylindrical walls defined by the through-feature can have channelsdefined therein that are designed to allow a continued and/orpredetermined amount of fluid flow around a particle once the particleencounters the through-feature. The fluid flow around the particle cancreate eddys vortices, and/or other flow patterns that better trap theparticle against the filter.

Certain embodiments of the filter can have features that allow thecapture of particles of various sizes at various levels of the filter.For example, an outer layer of the filter can capture larger particles,a middle layer can capture mid-sized particles, and a final layer cancapture smaller particles. There are numerous techniques foraccomplishing such particle segregation, including providingthrough-features having tapered, stepped, and/or diminishingcross-sectional areas.

In certain embodiments, the filter can include means for detecting apressure drop across the filter, and/or across any particular area,layer, and/or level of the filter. For example, in a filter designed tofilter a gas such as air, micro pitot tubes can be fabricated into eachlayer of the filter (or into selected layers of the filter). Suchpressure measurement devices can be used to determine the pressure dropacross each layer, to detect the level of “clogging” of that layer,and/or to determine what size and/or concentration of particles areentrapped in the filter.

Further, certain embodiments of the invention allow for fabrication offilters in a wide range of materials including metals, polymers,plastics, ceramics, and/or composites thereof. In biomedicalapplications, for instance, a biocompatible material can be used thatwill allow filtration of blood or other body fluids. Using certainembodiments of the invention, filtration schemes can be engineered asplanar or non-planar configurations.

Sorting

Sorting can be considered a special type of filtration in whichparticles, solids, and/or solids are separated by size. In biomedicalapplications for example, it may be desirable to sort blood or othertypes of cells by size and deliver different sizes to differentlocations. Certain embodiments of the invention can enable thefabrication of complex 3-dimensional structures that allow cells to besorted by size (potentially in a manner similar to that discussed hereinfor filters) and/or for cells of different sizes to be delivered throughdifferent size micro-channels or between complex 3-dimensionalstructures. Structures can be material specific and on planar ornon-planar surfaces.

Membranes

Membranes can offer filtration via pore sizes ranging from nanometers toa few microns in size. Membrane filtration can be used for particles inthe ionic and molecular range, such as for reverse osmosis processes todesalinate water. Membranes are generally fabricated of polymers,metals, or ceramics. Micro-filtration membranes can be divided into twobroad types based on their pore structure. Membranes havingcapillary-type pores are called screen membranes, and those havingso-called tortuous-type pores are called depth membranes.

Screen membranes can have nearly perfectly round pores that can bedispersed randomly over the outer surface of the membrane. Screenmembranes are generally fabricated using a nuclear track and etchprocess. Depth membranes offer a relatively rough surface where thereappear to be openings larger than the rated size pore, however, thefluid must follow a random tortuous path deeper into the membrane toachieve their pore-size rating. Depth membranes can be fabricated ofsilver, various cellulosic compounds, nylon, and/or polymeric compounds.

Certain embodiments of the invention enable fabrication of membraneshaving complex 3-dimensional shapes, sizes, and/or configurations madeof polymers, plastics, metals, and/or ceramics, etc. Furthermore, suchmembranes can embody redundant or non-redundant pores, and can befabricated to be flexible, rigid, and/or non-planar depending upon thematerial and/or application requirements.

Although the invention has been described with reference to specificembodiments thereof, it will be understood that numerous variations,modifications and additional embodiments are possible, and accordingly,all such variations, modifications, and embodiments are to be regardedas being within the spirit and scope of the invention. Also, referencesspecifically identified and discussed herein are incorporated byreference as if fully set forth herein.

What is claimed is:
 1. A system comprising: a first consumable ceramicnon-planar mold defining a plurality of spaces, each space from saidplurality of spaces at least partially bounded by a cast wall comprisinga plurality of wall surfaces; and a parent mold that defines a cavityconfigured to mold said first consumable ceramic non-planar mold;wherein: said cavity is substantially filled by said first consumableceramic non-planar mold; said cavity define a single demolding openingfor said first consumable ceramic non-planar mold; said demoldingopening defines a demolding direction in which said first consumableceramic non-planar mold is removable via said demolding opening fromsaid cavity of said parent mold with damage to neither said firstconsumable ceramic non-planar mold nor said parent mold; said cavitydefines a first cavity cross-sectional area that extends solely within afirst cavity plane that is oriented perpendicularly to said demoldingdirection; said cavity defines a second cavity cross-sectional area thatextends solely within a second cavity plane that is orientedperpendicularly to said demolding direction; said first cavitycross-sectional area is smaller than said second cavity cross-sectionalarea; and said first cavity plane is closer to said demolding openingthan said second cavity plane.
 2. The system of claim 1, furthercomprising: a channel extending through a predetermined set of castwalls of said first consumable ceramic non-planar mold.
 3. The system ofclaim 1, further comprising: a plurality of channels extending withinsaid first consumable ceramic non-planar mold.
 4. The system of claim 1,further comprising: an interconnected plurality of channels extendingwithin said first consumable ceramic non-planar mold.
 5. The system ofclaim 1, further comprising: a plurality of protrusions defined by saidfirst consumable ceramic non-planar mold.
 6. The system of claim 1,further comprising: a sub-cavity defined by said first consumableceramic non-planar mold.
 7. The system of claim 1, wherein: said firstconsumable ceramic non-planar mold is comprised of silica, alumina,and/or zirconium oxide.
 8. The system of claim 1, wherein: at least onewall surface from said plurality of wall surfaces is non-planar.
 9. Thesystem of claim 1, wherein: at least one wall surface from saidplurality of wall surfaces is anisotropic.
 10. The system of claim 1,wherein: at least one wall surface from said plurality of wall surfacesis isotropic.
 11. The system of claim 1, wherein: at least one wallsurface from said plurality of wall surfaces has a predetermined surfacefinish.
 12. The system of claim 1, wherein: at least one space from saidplurality of spaces has a substantially triangular cross-section. 13.The system of claim 1, wherein: at least one space from said pluralityof spaces has a substantially rectangular cross-section.
 14. The systemof claim 1, wherein: at least one space from said plurality of spaceshas a substantially square cross-section.
 15. The system of claim 1,wherein: at least one space from said plurality of spaces has asubstantially hexagonal cross-section.
 16. The system of claim 1,wherein: at least one space from said plurality of spaces has asubstantially circular cross-section.
 17. A system comprising: a firstconsumable ceramic non-planar mold insert comprising a plurality ofinterconnected channel molds, each channel mold from said plurality ofchannel molds at least partially defined by a corresponding cast wallcomprising a plurality of wall surfaces; and a parent mold that definesa cavity configured to mold said first consumable ceramic non-planarmold insert; wherein: said cavity is substantially filled by said firstconsumable ceramic non-planar mold insert; said cavity defines a singlemolding opening for said first consumable ceramic non-planar moldinsert; said demolding opening defines a demolding direction in whichsaid first consumable ceramic non-planar mold insert is removable viasaid demolding opening from said cavity of said parent mold with damageto neither said first consumable ceramic non-planar mold insert nor saidparent mold; said cavity defines a first cavity cross-sectional areathat extends solely within a first cavity plane that is orientedperpendicularly to said demolding direction; said cavity defines asecond cavity cross-sectional area that extends solely within a secondcavity plane that is oriented perpendicularly to said demoldingdirection; said first cavity cross-sectional area is smaller than saidsecond cavity cross-sectional area; and said first cavity plane iscloser to said demolding opening than said second cavity plane.
 18. Thesystem of claim 17, wherein: said first consumable ceramic non-planarmold insert comprises silica.
 19. The system of claim 17, wherein: saidfirst consumable ceramic non-planar mold insert comprises alumina. 20.The system of claim 17, wherein: said first consumable ceramicnon-planar mold insert comprises zirconium oxide.
 21. The system ofclaim 17, wherein: at least one wall surface from said plurality of wallsurfaces is non-planar.
 22. The system of claim 17, wherein: at leastone wall surface from said plurality of wall surfaces is anisotropic.23. The system of claim 17, wherein: at least one wall surface from saidplurality of wall surfaces is isotropic.
 24. The system of claim 17,wherein: at least one wall surface from said plurality of wall surfaceshas a predetermined surface finish.
 25. A system comprising: a firstconsumable ceramic non-planar mold insert defined by at least one castwall comprising a plurality of wall surfaces; and a parent mold thatdefines a cavity configured to mold said first consumable ceramicnon-planar mod insert; wherein: said cavity is substantially filled bysaid first consumable ceramic non-planar mold insert; said cavitydefines a single molding opening or said first consumable ceramicnon-planar mold insert; said demolding opening defines a demoldingdirection in which said first consumable ceramic non-planar mold insertis removable via said demolding opening from said cavity of said parentmold with damage to neither said first consumable ceramic non-planarmold insert nor said intermediate mold; said cavity defines a firstcavity cross-sectional area that extends solely within a first cavityplane that is oriented perpendicularly to said demolding direction; saidcavity defines a second cavity cross-sectional area that extends solelywithin a second cavity plane that is oriented perpendicularly to saiddemolding direction; said first cavity cross-sectional area is smallerthan said second cavity cross-sectional area; and said first cavityplane is closer to said demolding opening than said second cavity plane.26. The system claim 25, wherein: said first consumable ceramicnon-planar mold insert is comprised of silica, alumina, and/or zirconiumoxide.
 27. The system claim 25, wherein: at least one of said pluralityof wall surfaces is non-planar.
 28. The system of claim 25, wherein: atleast one of said plurality of wall surfaces is anisotropic.
 29. Thesystem of claim 25, wherein: at least one wall surface from saidplurality of wall surfaces is isotropic.
 30. The system of claim 25,wherein: at least one wall surface from said plurality of wall surfaceshas a predetermined surface finish.